I'm not big on picking favorites because my favorite knife is usually the one I have in my pocket that day. Seriously, I like them all or I wouldn't have them.
I currently 3 PM2s. Cruwear, Red M390, & black DLC S30V.
The Cruwear is probably my favorite. I like the edge Cruwear takes, the grey scales are nice, and the action is perfect (strong detent, etc).
The red M390 is newer to me but it's quickly gaining on the Cruwear. The G10 is grippy and I like red. M390 is fairly new to me but, based on use and sharpening of my PM2 & Para 3, it might just be my favorite stainless steel. The action isn't as nice as my PM2 Cruwear but it's not bad either.
The all black S30V knife was my first PM2. I bought it used off the Exchange and it's been great. I reprofiled the edge to 15 dps and it's sharp as can be. It's well used and not as exclusive as the other two but it's served me well. I think I've carried and used it more than the other two combined.
Ask my about my favorite Para 3 and you'll get pretty much the same answer.