the iron horse mkIII is a real good bike/frame. the maestro is somewhat similar to the dw_link, or so they say, and everybody raves about the dweagle link, so pedalling performance etc should be similar. the mkIII has five inches of travel, can take a few knocks. i saw a picture recently in the mtbr iron horse forum of some dude winning a downhill competition on the mkIII (apparently he was still waiting for his IH downhill set up) so im sure there is no question about how tough it is.
the trance is a 4" travel bike, so if you want the shorter travel, then thats a real good frame for sure and with a good suspension system. some people though are worried about the shock placement on the newer frames. if you go to the giant forum at mtbr im sure you will get a more accurate picture to that issue.