Handling could have a lot to do with stem length, too...a shorter stem will = more sensitive, "twitchy" steering, longer stem will make steering less sensitive.

My current bike originally had an 80mm stem...and the steering was a little scary on an already stiff, aggressive frame. I felt a little scrunched in the cockpit, too, so my LBS swapped out for a 100mm stem and the difference in steering feel was pretty marked. If these bikes you're testing all have different length stems that could account for a lot of the difference you're feeling in terms of handling.