I prefer a 50/34 double chainring and a big mountain bike cassette, personally. I really have come to rely on my Shimano XT derailleur, so I'd rather have the bulk of my gearing in the back and keep the front simple. I end up spending 80% of my time on the larger chainring anyways; I've worn through my second and will soon be on to my third, but my small ring is still fine.