I have a 425, which is a 426 with a Snody wharncliff blade. I like it a lot; the ergos are excellent and the lockup is extremely solid. I'm not a linerlock fan in general, but my 425 locks up almost like a framelock. And it's a very stout, but sharp blade.
The only MOD I have is a Razorback, can't help you there.
I'd go with the 426, if only because in a couple years the G-10 will still look great, whereas the aluminum on the tempest will probably look pretty beat. It'll still be solid, though, if you don't care about looks.
I will add that in my personal experience, Benchmade has the most reliable production liner locks of the companies I've owned. Never owned a MOD linerlock though.
