I have only the SOG Powerlock, which I purchased after having owned (still do) the SOG Power Plier. I do not have the Leatherman Wave, nor have I handled one.
That being said, I am very impressed by the SOG. The compound leverage works very well as stated in the precious post. I have owned several of the Leatherman type tools since their inception and have broken all but the Power Plier and PowerLock.
Another really good thing about the SOG is customer service. I wrote to them about a dissapointment with the wire cutters in the Powerlock. They replied, I sent it back, they fixed it to my specifications (they had modified the design a little from the Power Plier in order to satisfy a wider range of wire cutting ability). Now I have a tool which works great for what I need (BTW, they sent me a loaner while mine was being fixed).
I can't say enough about the SOG Powerlock. It's been the best working tool for me so far. I highly recommend it. If you are looking for an all in one tool (I also carry a couple of knives, so I don't need that particular feature), maybe the wave would be more adequate. But, for me, the SOG works very well.
My .02,
Ed