I usually carry my small micarta BG42 in the leather pouch during the week, and clip the large swedged regular BG42 on my pocket on the weekends. I have a few similar sized Bucks (also BG42, go figure) that like to creep into the rotation on occasion as well.
I started with a small regular, and loved it. Later got the small micarta and large reg at the same time, and the small regular never saw any action after that. I REALLY think it all comes down to what fits your hand better and what you feel you are comfortable with. I would trust any of them to handle just about any job that I could come across. The large definately feels like a tank compared to the others, and its just the grip it gives not the solidness of the knife itself, but if I had to go with just one it would almost definately be the large swedged regular.
If you are in an office environment all the time and rarely make it outside, the small will be more than enough and won't make so many people think you are crazy. If you work and play outside all day long all the time, I would go with the large.