I think that you will find everybody has their own favorite size and combos. If I was to guess I think most run a larger front tire such as a 2.4 and 2.25 rear(just a guess). Myself, I have a WTB WW 2.55 front and rear on a 29er hard tail. That being said a lot more has to go into consideration in which tires to run such as local terrain, tire clearance, and of course your wallet. I would hit your LBS and pick their brains in regards to what they and others are using in your area.