I was in a similar boat : iPhone user for many years -> Android for a couple -> tried out the 6S -> went back to Android and gave the 6S to my wife.
Of all the Android phones I could have, my current is a Note 5 (and I had promised myself that I would never buy a Samsung product after Note 3!). The reason I went back to Android was simple: choice!
A few examples:
1) Need to stream your music library? With Apple, buy their expensive-for-what-it-does airport express. With Android, buy the 35 bucks Chromecast! You can buy 2 for 50 at Target.
2) Need a stylus? iPhone - out of luck. Android - Hello Note 5!
3) Need OIS ? with Apple, only the expensive-for-what-it-does iPhone Plus models have it. Android - most top end models that are cheaper than the Plus model have it
4) File system ? Enough said!
5) Don't like the look ? Apple - you are looking at it the wrong way. Buttons are supposed to look like text! Android - whatever suits your fancy man! Themes exist on Android and I love it! I have dark backgrounds all over my phone courtesy a theme and I can use my phone so easily in the night...without lighting up the whole room!
6) Too high price ? With Apple, you just need to suck it up. With Android, many retailers have good deals even for the current flagships during the holiday season. Case in point, Galaxy S6 32GB for 400 on Amazon
7) Multitasking: Benchmarks say that Apple's processor is in a class of its own! Pity then, that it does not support true multitasking. Case in point, my wife was sharing a big video captured via the iPhone camera to a whatsapp group. Since it was taking time, she went to another app hoping this would continue in the background. Guess what, the uploading just stopped and she had to baby-sit the process.
Android supports true multitasking. This is really great but can also be a curse when some rogue apps continue to run in the background. The onus is on us to manage this.
What I miss:
1) iOS 9 is really smooth on the 6S. I expect iOS 10 will be too. After that, Apple will give you the "free" upgrades that so many here are so proud of and that will eventually slow down your phone to a crawl!
2) Awesome browser in Safari. Nothing on Android comes close in terms of how smooth and fast the browser is
3) Syncs your iTunes library without any third part libraries.
4) In-built, offline dictionary, easily accessible from anywhere in the device. Why Android does not have it, I do not know yet but I use a workaround that serves the purpose.
I know, pretty soon I will be pissed off at Samsung for not providing an update to my Note 5. But I will remind myself how my 3G/3GS was screwed by Apple or how the users of 4 and 5 regret upgrading to iOS 7,8 and 9. Anyway, I change my phone quite frequently (even though I got a feeling that the Note 5 is a keeper) and I do not think this will be a problem.
For what the Note 5 provides today, it is definitely better value for money than the iPhone. I am pretty sure you will find many other Android phones that are value for money. However, I have noticed that in the quest to get the most bang for the buck, people tend to buy alleged flagship killers and then get disappointed when the camera is not up to mark (or <insert another feature here>) and then run back to iOS thinking it is the best platform. You should give Android a fair chance. It is improving by leaps and bounds - faster than Apple is improving their iOS platform