I'm surprised no one has mentioned a large Buck Pro Vantage. I can get all fingers on it (just right), and I wear L to XL gloves. It has s30v steel (you can see if you like it) - one of the nicest steels available. Buck has one of the greatest warranties in the business - lifetime warranty. They actually replaced a broken tip Buck 110 for me this past summer free of charge. The Pro Vantage's drop point blade hollow grind is a great blade shape, and the flipper works well for fast opening while the thumbhole works great for slow opening.
The earlier Vantages had trouble with blade centering issues, but that was when they came out two years ago. Nowadays, the centering is great (mine is), and if you do happen to get an old stock (unlikely), you can send it to Buck and get it back in 4 weeks all fixed up.
I love my Buck Vantage Pro. Fantastic size in my open, great pocket clip, fancy G10 handles, the new best steel s30v, all for $60 - nearly half the price of a Spyderco Paramilitary 2. I have also heard that Spyderco does NOT have free blade replacements - maybe you care about looking into that? The Benchmade looks good, too. The ZT is assisted-opening, I think, so it's a whole different kind of beast than the other three - if that's what you're looking for. I would say for a manual folder go for the Buck Vantage Pro or Benchmade Grip FIRST because of the lower price tag, you can get a feel of what you like. If you want an AO go for the ZT or an s30v Blur.