I suggest glasses. Slightly larger screen will not help aging eyes. No, Apple will not give you a larger screen unless they figure out a way to make a 4.3 incher with the same forum factor with the iphone 5S, and that small of increase will not be good for aging eyes either. Nor will a 4.5 inch screen.
The only reason I am looking forward to a non-mechanical home button is because it seriously limits the design of the phone. Otherwise i would say mechanical is best
I've owned a couple of androids that have capacitive buttons... they suck. You push it... maybe... did it register? better push it again... damn... I pushed it twice... Screw it