Personally, no.
While I do prefer a smaller phone which is why I still use a 5S (although I might go buy a 6S this weekend) I MUCH prefer the 16:9 aspect ratio. 3.5" with a 16:9 aspect would be too narrow for me, and most people IMO.
4" is a good compromise between still having a small phone while also having a standard aspect ratio. Again, my opinion.
While I do prefer a smaller phone which is why I still use a 5S (although I might go buy a 6S this weekend) I MUCH prefer the 16:9 aspect ratio. 3.5" with a 16:9 aspect would be too narrow for me, and most people IMO.
4" is a good compromise between still having a small phone while also having a standard aspect ratio. Again, my opinion.