I'll be the odd duck (or beaver) and cast my vote for the Benchmade 300SN. You live in Portland, so if you ever have a problem, Benchmade is right down the road. That's one of the chief reasons I own so many! Problem solved in a day or two, and nothing gets lost in the mail. Also, Axis Lock is by FAR the best lock of the bunch.
ZT is out because I abhor recurve blades.
Spyderco makes a hell of a knife (I EDC a PM2). I've never held a Spyderco flipper, but every Spydey I've ever handled has had more drag on the blade than I think should be there. In a flipper design, that's the Achilles heal. BUT, maybe they worked magic on their flippers, making them less draggy than their other designs.
Spyder