Yeah rentals are out of the question, hell having the bike in stock that I want to buy is tough. This is a small town so they dont keep in stock alot of the higher end models. I sat on the entry level Superfly100 yesterday and it felt pretty good, going to go by the specialized shop today or tomorrow to see if they have something similar to the Stumpy or Camber to try and compare. I do like the colors of this years Specialized so maybe that will be a factor as well.
The hardest part for both brands is if I should spend an extra $250 for more travel. All else seems identical.
I've posted the same thing over and over in these types of threads. Take the time to travel and demo! It will save you a ton of money in the long run.
I'm selling a 3k Stumpjumper 29 Comp with less than 100 miles on it, because I didn't demo it first. I wasn't happy with it. Walked into the shop where I bought it and they had gotten in a TBc and TBLT for demoing.
Once I tried the SC Tallboy, I didn't want to ride my SJ anymore. You don't want to end up where I'm at. A few calls and a little bit of driving around would have saved me a bunch of money and gotten me on the right bike the first time.
As far as the Trek and Specialized you have in you list, 2 things I don't like about both are the proprietary shocks. After trying to upgrade the shock on my SJ, I'll never buy another bike with a proprietary shock again.
At least with Niner, SC, Intense, Pivot, Mojo etc... all use standard shocks- yes the tunes are different, but they can be replaced/upgraded easily.