20" Pros : Lighter,Easier to Throw, Lesser Stuff to Break 20" Cons : Harder to roll up on roll off obstacles (smaller wheelbase). The 20" is great for someone who has been riding 20" their whole lives, its an active bike, easier to throw around. Great for smaller frame sized rider like me! 26" Pros : Rolling becomes much easier due to the bigger wheelbase, more distance covered 26" Cons : Heavier,A lil more stuff to break,not as flicky and throwable as a 20". The 26" is great for people riding mtbs all their lives. Much easier to balance on them. Its all based on personal preferences, both have its good and bad points. I prefer the 20" over the 26" due to my small frame short human body. But i love the feeling of being able to balance extra stable and being able to roll off lotsa obstacles on the 26". Especially since i roll alot. For a beginner i recommend a 20". Slightly cheaper, Easier to learn on it, though it may be a little active, you'll get used to it after awhile.