There are a number of reasons for this.
1) Most of my family have them and being able to find them view iPhone finder, will be very useful.
2) iPhones seem to be better constructed and supported by Apple for longer.
3) Android just seems to be too "techie/geeky", if you know what I mean.
However, the problem is my ideal iPhone does not exist yet. While the 4S is great and all, the screen is just a little small for my failing eyesight. I cannot read the text under the icons without my reading glasses on. So I am hoping that the next iPhone will be just a little bit bigger, but not too much.
NOTE: If you can have a larger font for the text under the icons my problem would be solved.