Hi James,
I took a look at the bikes you mentioned and it's not an easy decision to make
If you compare the specs, probably the GT Avalanche is your best bet, though the other bikes have quite similar setups - all have forks with 100mm travel, hydraulic disc brakes etc. What I would suggest you to do is to go to a store and sign up for a test ride. Bike geometries can be really different, you should go to a store and take them out for a quick spin to see which feels the best, the most comfortable. Hope this helps.
Cheers,
Balint @ Evans Cycles