The traction of the TW tires offroad is quite amazing, but the suspension in stock form leaves a bit to be desired. I can't speak for the other bikes, which may be better sprung, but the TW lacks a bit in that department without some tuning.
The stock gearing on the TW lends itself quite well to riding offroad as well, but whoever told you it lacks a bit on the highway, well, they're right: secondary roads with 55mph speed limits are fine, but the freeway/interstate would be a lot too much for the bike. Some people seem to have good luck doing it, though.
The fact that the TW has a reasonably low seat height, good gearing, and really decent traction makes it a great choice for offroad use. All of the bikes you mentioned (including the TW) can be built to do much better on or offroad, depending on your preference. The factory configuration is a compromise, attempting to get the best of both worlds, and they don't always hit the mark with their compromise.