I have a para 2 and had an REI grip. Both fantastic knives, I just like the way the para 2 carries better, slimmer in the pocket. However the G10 handles on the grip are leaps and bounds nicer than the plastic handles on the regular models, and the S30V steel is the icing on the cake.
I'd go for a para 2 if you want a slimmer knife that feels more secure in the hand.
Griptilian if the thickness doesn't bother you, it is a bit slippery though the G10 is milled and smooth.
Military is too big for me, plus tip down is a no go.