it's a Transition for sure --- for one, you can see the TRANSITION on the down tube and Diamondback and AirBorne, although they look similar, they're clearly not. Transition is built with quality parts and linkages, can't say the say for the other two... they're the supreme definition of "knock off".... kinda funny, on the Airborne, man, did they botch the seatpost, tail-end intersection... it's like an intern was in charge of the mock up.

 late follow up to my comment --- I ended up buying one of those DiamondBack DB8's --- the company where I get them, they also sell Laperrier, which is what I really wanted but, the model I want (DH 727) is sold out for the season and the 2016's are a ways away --- shits N giggles, I got the DB8 just to hold me over and, my sales rep gave me a great bro-deal on it. Anyway -- geeez, I'm really impressed with the DB8 --- whatever it is about the rear linkage compared to the Tr500, I don't know but, man... the bike kicks butt. and get-this, it climbs really well too. Sure, climbing on a DH isn't something you normally do but, I do... we ride lots of trails where climbing is a must. DB8 can handle climbing very well (if you look past the fact it's 10lbs heavier than your typical enduro or XC).