Research each bike, the specs of the components, and then go ride each to see which bike feels the best under your weight. All 3 are from reputable companies known for mountain bikes so any of the three of them should do the job that you want them to do. Riding style and trails types to be ridden also play a key role in the selection of a mountain bike.
2013 Specialized Carbon Camber Pro 29er (Warranty frame and other stuff)
2011 Specialized Stumpjumper Comp 29er
The fork specced on the Trek and Spec is a Suntour designed for dirt bike paths but unable to handle trails or your 250lbs. A bike with an air fork instead of an undersprung coil fork is what you should look for. Or you can change out the Suntour for an air fork from a place like bluesky-- Recon Silver is $210. Used is also an option.
The Giant Talon 2 has the Recon Gold air fork you need.
I ride Treks with no problems whatsoever, except that my last one was stolen from my garage (et tu brute!). I have to be fair though, the fork that you'll find on that Marlin is complete crap. I still ride with it under the assumption that it will one day make me more appreciative of what I have and generally make me a better rider. Some people may call bull**it on that one, but hey, maybe they're Douc*enozzles. Your mileage and preferences may vary.
"Faster, Faster until the thrill of speed overcomes the fear of death." - Hunter S. Thompson