20 or 26... i went for 20 as my mate insisted it was easier to learn on.....he was right ive progress pretty far in a few week only problem is i get chronic back ache at the start of the ride as i,m jus shy of 6ft but i do find it ez to throw the bike around being so tall on a small bike and i reckon on 26er i would of felt a little unstable trying some of the moves i do ... hope it helps ....M-