I'm an avid Android/iOS guy user of both platforms and to be honest can't really complain with both. If I was to look at it this way from history:
So the iPhone 6s+ in Rose Gold (do not ask why. I wanted something entirely different) is my first iPhone since the 3GS! But then I decided to go to android after my 3GS broke down on me because... why? is what most people would ask:
1)
Screen Size; iPhone 4 to iPhone 5S had very small screens at a measely 3.5 and 4 inches.
Android on the other hand offered a 5.0 inch screen in the form of Galaxy S4.
After playing around a lot I seemed to like the bigger screen and I did not miss the one-handed use of iPhones as I found 2-hand typing I was able to type even quicker and with the added Swype functionality helps me to be 1 handed while I'm lazy in bed so I can simply drag letter by letter.
Even when iPhone 6/6+ came out with the upsized screens which I wanted, I still didn't feel convinced because the price points were very high at that time for me and yet only change was the screen and a processor. By then still not so convinced despite Apple putting up larger screens and my Android devices still perform perfectly as of that day of announcement.
2)
Customizability; I love experimenting with devices as I'm enthusiastic to see what is right for me. Some widgets that benefit me a lot were Weather, Music. iOS at that time was a bit too bland with features at that time and lagged behind android as a whole in terms of offerings, it was too simple yet hard to justify at that time the price point.
3)
Notifications was also a big selling point. This is where the android OS nails it well. By being able to monitor notifications icon at the top you know what apps have things waiting for you to see and also it's well grouped up. That way you don't have to dive in so deep to venture through each app.
4)
Rooting was something I like to do back then. I was very experiment-oriented when it came to tech and android would let me do that. I get to mess around and drop files in and out like as if it was a portable memory drive. I got to customize the OS as I didn't like touchwiz.
So then after my S4 has passed 2 years or so it started dying and slowly lag and battery wasn't keeping up well after so many uses, I got the Samsung S6 on contract, and it only lasted me less than 4 months and as a result I bought out the iPhone 6s+ 64GB in Rose Gold outright, in some ways this is a good timing of the iPhone release... Why did I sell my S6 so quick in favour of iPhone 6s+?
1) Not entirely relevant but Samsung announced price cuts and even official 3rd party sites in Australia recently [genuine resellers] were cutting the price down quickly [700AUD maximum now]. If I waited longer then the resell value of S6 was lower and I won't get much money left back in a quick amount of time period. Now some might argue resetting would work.
2)
LAG/delay/stutter. For a flagship like the S6 with high end specs you'd expect it to be not so laggy right. Not until I had to disable a lot of animations, but even so disabling all those fancy animation, it still had extreme amounts of stutter, lag and this was 4 months in out of 24 months of usage. What would it possibly be like if I was near beyond 1 year, probably the experience would be horrible.
3)
Battery drain is ridiculously fast despite the bigger battery [near iPhone 6s+ capacity just abit lower]. Probably attributed to the quad HD screen, and also sometimes Android [touchwiz] inability to manage processes and apps well enough. Sometimes I can't even last beyond 3 hour screen on time on a moderate basis on this and it sorta frustrates me a lot and usually it would die after 5-6 hours of usual use with 2-3 hour screen on time.
4)
Heats up very quickly [in relation to point 3]. By then I starte seeing things not so normal... Even with MINOR [not even mention games which are intensive] applications, it heats up pretty quickly and I get annoyed by that. If it heats up this bad during minor app use I can't imagine what gaming feels like. Very hot, and a severe and fast battery drain.
So sold the S6 quickly and bought an iPhone 6S+ immediately the day after it was sold. Why iPhone 6s+?
1)
Operating System I was convinced by the performance of the iOS system after using iPad Air 2 for awhile before as my main driver [while i was using android on the phone part of things], it was so fluid and smooth and virtually never lagged up on me, android in particular started lagging up in the early months which i couldn't accept and like. With iOS 8.4 and iOS 9.0/9.1 have totally added so many new features and they have refined the experience much more which really. In contrast to android I noticed it never never has any lag or stutter which is very impressive and the A9 chip [which has shown greater advancement over the A8] has convinced me to jump over in real life use as a whole and lab tests which although interesting, I dont take too seriously. In the long run iOS "copy" other features, but it surely is better and seamlessly integrated with the whole system.
Now before I did say I love customizing but that was only because I was very free before then I had so much time to mess and play around with phones exploring potentials, but now I'm nearing end of my uni studies, time is short for me I don't have a lot of free time to mess around so I wanted something that just works out of the box without too much worrying. iPhone 6s+ did that for me.
2)
Camera seemed right and easy to use. Found Galaxy S6's selfie camera although wider I feel it applies too much smoothing onto the final image which causes detail to be lost and a very artsy effect... with a lot of blur. The rear camera was good on S6 if not near equal to the iPhone 6s+ however I really wanted to mute that clicking sound as it was very loud and annoying and I couldn't get it off. With the iPhone I can have it silent and no more unusual clicking.
To be honest I find no difference and I do professional photography too for a part time thing with my actual camera so it's hard for me to nitpick very slight differences between these two cameras, however the iPhone camera is so much easier to use which is what I want for a portable camera in a pocket if I need it. For any extreme adjusting I have my other camera for that.
3)
Battery Life is what I like about the 6S+ over the S6 more imo. A 1080p screen [now I know why Apple doesn't go quad HD] is pretty sharp to my eyes already, and it was hard for me to discern the slightest difference between quad HD and full HD 1080p as the differences are very small. The 1080p screen seemed right, and the combined optimization of iOS along together is what makes this stand out for me. I was able to get easily 8-10 hours of usage time with this which wasn't possible with my previous phone which only gets me around 3-4 hours usage time with a similar sized battery. Not to mention it would heat up so much that it gets annoying to hold.
4)
GAMES run smoother. And this is a no brainer. I don't really know how to explain it, you just have to see it yourself. Virtually when I try to cram so much data the iphone seems to work magic and won't lag at all despite so much data being processed in a shorter amount of time [in this case fast forwarding]... Previously the S6 would lag so bad with intensive graphics it was a total joke imo...

The very small fps was what sorta killed me too with the Samsung despite the specs it wasn't optimized properly paired with a very super high-res screen.
To this date I have played Vainglory and Rival kingdoms, two strategy-based games which had high intensity process and rich graphics and my iphone 6s+ handle it very well yet it didn't really heat up at all. not as bad as the samsung s6 did but this was what surprise me a lot.
5)
Screen Size finally [and of course] iPhone joins the big league with two different screen size and this was what I wanted in iOS phone. No explanation needed really but I think quad HD screens in current android flagships mean more pixels to power up and run and can prove to degrade performance as a result and also may result in quicker battery drain because more pixels = more power consumed... I found either iPhone 6s or iPhone 6s+ screen to be pretty damn sharp already and don't really miss quad HD and amoled display in the s6. Also in relation to point 3, battery life seems to be better as a result paired up with the OS integration and optimization.
There are more reasons but I don't want this post to be too long else it might get removed, so here are some main points why I would change and some could probably relate.
Summary; I grown tired of customizing and rooting phone to get it to work. Even jailbreaking wasn't a necessity it was just an option for extra features but I felt those extra features were not beneficial to me. I wanted something that just works out of the box and iPhone did it well for me. Didn't have to go on a massive hunt to disable things that I didn't need, I just knew it works and I won't really complain about lag/stutter/poor performance/heating issues.
As a result I'm very satisfied with iPhone 6s+. But don't get me wrong I do miss something from android like the notifications icon on top which prove to be very useful. But however the lack of lag and stutter, primarily is what make me want to switch and I can see why Apple is so locked down and restrictive, by doing so it is able to control and make the experience much more smooth and refine.
So yes I don't hate either operating system, it has it's pros and cons and I like both. However I felt too convinced by the 6S+ performance as a whole when I tried my friends phone first before making the switch. Sure it look same as iPhone 6 as most people would say, but still I'm not about looks I'm about how it works and it just works seamlessly.
I'm not trying to be an Apple fanboy. I just want to be honest and clear to all the viewer here so they have some "Idea" on both sides.