Usually the S model isn't a significant upgrade from the non S models
For me the S models aren't a significant enough internal upgrade to make the switch.
Perhaps not for you, but as C DM stated they are in fact significant tech upgrades.
If one is going from numbered to numbered models, say 3G to 4 to 5 to 6, then that is fine - those all represent big upgrades not only in form factor and feature set, but also case redesign. Those are also big tech jumps imo. Perhaps arguably less so with 6 vs 5, but the 5 vs 4 and 4 vs 3G were significant upgrades.
But that doesn't mean people who choose to upgrade annually or with "S" models aren't getting better phones in their own right.
Where I was coming from, when I bought the 6 was from a 5s. Techwise, the 5s to 6 is a marginal jump. 6 is faster, yes. A8 is faster and more efficient, yes. But minimally so compared to what the A7 was to the A6. I believe Apple in their presentation stated the CPU is only 25% faster? (edit:
http://www.engadget.com/2014/09/09/iphone-6-a8-chip/) Which is by no means a generational leap, and for me not worth the 1000$ I spent on launch day. If you are familiar with benchmarks, you'll see the S models are indeed significant tech upgrades
Most often, it is the case-redesigns tend to be marginal techwise (relative to the previous S model): The iPhone 3G was essentially the original iPhone repackaged with a 3G radio. The 4 used essentially the same chipset as the 3GS, only clocked higher and double the ram (and in SOC design I believe) but it was also pushing a Retina display, whereas the 3GS was not.
I suppose the exception here is the iPhone 5, which did bring a very nice tech bump from the 4S (twice as fast I believe) alone with LTE and redesign. But in every other case, I don't think one can say the "S" models are not significant.
The 3GS blew the 3G/OG-iPhone out of the water speed wise when it came out. The 4S had 2x the CPU and up to 7x the graphics power of its predecessor. The 5S brought 64-bit architecture to smart phones and had more than twice the performance in benchmark tests as the 5 did.
Every iphone model, every year comes with feature upgrades so we can disregard that, but look solely at the specs and you will see the S models represent the big jumps tech wise. How else is Apple able to make them appealing to the market if they are not in new cases & form factors?
Not everyone will share the same opinion and that is fine, but I doubt I was the only one disappointed with the minimal tech upgrade the 6/6+ brought. Considering the small performance jump, plus with the same amount of RAM (yet pushing larger, higher res displays - ever notice anyone complain about their 6+ being laggy relative to the 5s?) coupled with the buggy disappointment that was iOS 8, it should not be difficult to understand why many are looking forward to what the 6S may be and also what September has is store
You think your phone is old? Im still using a 3GS as my daily driver.
Just replaced the screen and soon the battery. (It doesnt quite need a new one yet, but its getting there) That should add another 5+ years to its lifespan
Wow! This is pretty incredible. I have some questions if you don't mind - What has been your experience over these years? Why did you decide not to upgrade? What iOS is it running on? Why the 3GS? How do you find the battery life?
Thank you
I just purchased a 3GS myself, it was still sealed in the box - 8GB but only $72 Canadian! Nice back up phone if need be.