You simply can't go wrong with either one. There are two distinct tradeoffs, as I see it, and neither one is a dealbreaker in favor of the other, though personally, I lean towards the PM2:
Paramilitary blade-handle ratio. For some, this is a downside. For myself, it's one of my favorite aspects of a lot of Spyderco's line. It looks funky in pictures, but once you hold one, any concerns will melt away. The handle is impossibly comfortable, just the right width, and the length just makes so much sense once it's in use. You can grip the PM2 in a number of positions and each one conforms to the contours of your hand and fingers. I haven't owned mine long, but it's become one of the most comfortable folders I've ever used. The finger choil is so choice. If you have the means, I highly recommend picking one up.
Griptilian handle material. This one is fairly polarizing, and judging from these forums, typically, you either love it or hate it. I don't care for it. As mentioned above, it feels "cheap" in comparison to many other folders, some costing much less. The overall design is quite comfortable, with no irritating hotspots and a smooth and reasonably narrow grip. Despite the lack of a blade choil, it's easy to choke up on the spine of the blade with your thumb, for a secure and accurate grip (though, as with some of my other folders, I tend to
want to move my finger into a choil that simply isn't there). I just don't like the plastic itself; it feels thin and squishy, like it might crack if dropped or bumped too hard (though this never happened to any of mine in the time I had them). Getting back to what I was saying about the PM2's handle, I just wish the Grip's was a little longer, so my pinkie had some room to hang out and reinforce my hold.
Locking mechanism on each is great, and both are super secure and easy to engage and disengage with one hand. I prefer the narrower tip of the PM2, as it pierces very well and is quite capable with fine tip cuts, like in wood.
But really, go with your instincts. You definitely won't regret whichever you choose; you'll find it compulsory to purchase the other eventually.
