Here's my philosophy.
1. Why limit yourself?
It's the same thing as saying "buy as much truck as you can afford." If you have never had a truck before, you can't possibly understand how stinking useful they are. Buy a compact truck, and I almost guarantee you will wish on a regular basis you had that quad cab diesel 3/4 ton......(until you get to the pump)......when you start wanting to buy landscaping stones, pull trailers, etc.
I'd rather carry an extra inch of blade, and considering legality of knives in my area is 3.5", I just carry knives that are that length. I might not NEED it, but then again, I might. If I don't have it, I promise you I will wish I did at some point.
2) The knives I appreciate are generally larger because I have large hands. I like strong knives because I tend to use them pretty roughly at times, especially when I work on the house, or go camping (which I do pretty often). I carry pretty much the same knives everywhere, and my profession is outdoorsy so my stuff tends to get used/carried a lot.