I own both models. I prefer the Signature 2 due to the fan and heatsink design. The Signature 2 card runs cooler than the FTW and is nearly silent at up to about 63% fan speed. I have found 60-65% fan speed to be sufficient to keep the Signature 2 running at 66C or less. The Signature 2 does exhaust quite a bit of heat out through the backplate. Some heat exhausted from the rear fan will go into the case, but I have not had any issues with this. The Kepler cards do not run all that hot to begin with. However, if you plan to run the cards side-by-side in a tri or quad configuration, then the FTW cooler design may work a bit better due to all heat being exhausted out through the backplate. Regarding the Vapor Chamber cooling of the FTW, I tested this card against a reference card with reference cooler and the load temperatures were almost identical. Perhaps the Vapor Chamber cooling was more beneficial for the Fermi cards but with Kepler, I was not able to find any difference temperature wise.
 
I think either card will handle Skyrim or Far Cry 3 just fine. I play both these games myself from time-to-time. Depending on resolution, Far Cry 3 can benefit from a second card in SLI for the most optimal framerates.