What Schwalbe Nobby Nic should I buy? I recently bought a Swissbike X5 (same as the Montague Paratrooper, but labeled Swissbike and matte black).

It came with Kenda Kinetics 26" x 1.95" (front and rear)  that I'd like to replace.

Due to good experiences with Schwalbe, I'd like to buy the Nobby Nic, but there are many different Nobby Nic models, as well as widths. 

I'm going to use the bike mainly for fun riding in the forest.
I would go with something in the 26x2.25 range with the Double-Defense protection.  The 2.25 will give you nice volume to allow lower pressures while still being narrow enough to fit most frames (you might have to go narrower if your frame won't allow the 2.25).

Double defense will give you the maximum protection, it weighs more, but I doubt you would notice unless racing.

Unless you are well versed in running tubeless, I would just stick with tubes.

Hope this helps.