I agree that after riding a 29er, 27.5 can feel small. But, as several folks have said here, it depends how tall you are and what kind of riding you do. I’m 5′ 11″ and I really like my 29er hardtail for cross-country style riding. For shorter riders, I think a 29er can be a stretch. For all-mountain riding, the difference isn’t as clear to me. I recently ran across this page that has a pretty good discussion of the pros and cons of various mountain bike wheel sizes: http://www.cheapbikes.org/mountain-bike-wheel-size. Happy trails!