The 0550. Its a good cutter plus its not as heavy as everyone says. I carry it at work along with a tool belt, radio and a wad of work keys and I don't feel the extra weight of the knife at all. The pm 2 is almost too light for me, but that's personal preference. Plus the 0550 will probably outlast you. I have both knives, and I like the pm2 very much but I love my 0550. Plus you wont be able to get the 0550 forever as they are discontinued, I doubt if they will ever stop making the pm2.
Ditto. Mine doesn't feel like a brick in my pocket.