I have never test ridden a frame and they are all good. As someone said above, by the time you've put a few different bits of kit on it will feel different anyway, unless it's off the peg.
Weight of tyres and wheels
Size and pressure of tyres
Suspension setup (assuming the forks are the same as they have different A-C heights for the same travel)
Stem length and angle
Number of spacers
Seatpost layback
Saddle position
Bar width, sweep and rise
I've ridden other peoples bikes with different setups but essentiall the same. Some I hate, some I love.

