I ride 700c, 29er and 26". My favorite is my 29er. 700c is definately faster on gravel but I would rather sacrifice a little speed for more comfort and fewer flats. and my 29er holds speed better than my 26". But I like and ride them all.
700 for smooth southern Minnesota and Iowa. 650b for bigger rocks up north - more air volume is nice because it lets me run a lower psi and still have plenty of air space between rim and ground.
