I've had 'em both. Still got the Mini-Pitbull, although the F4 has long since gone away.
F4 was just too damn lil' and the sheath provided with it is too damn bulky for the knife.
The Mini Pit is small enough to be VERY handy, but large enough to handle some pretty serious tasks. Also, I got kinda big forepaws, and the Mini Pit fits 'em quite well for a small fixed blade. It's actually one of my favorite knives, and travels with me quite often on days that I decide my Spydie Perrin is a bit too much.
One of the best things I've done with this one was to cut off that cheesy lil' clip on it, and mount a Tek Lock on it for horizontal carry. Took less than five minutes and made the carry MUCH better.
Matter of fact the day after I brought my own Mini Pit home, the wife had to have one too. She still carries hers more often than not when she's out jogging.
I'd suggest the Mini Pit. I doubt you'll be disappointed.