I’ve got two 26 and when I tried a 29 I was amazed at how far and fast it rolls and what speed I could manage not only on my local trails but on the roads getting to it. I ended up buying a salsa spearfish and with the small travel and big wheels I’ve never been as fast. Although I’ve now found fat love and it does seem to be the other end of the spectrum, lots lots slower but equally as much fun . So I would agree that 29ers are a huge difference but I haven’t tried a 650b and doubt that a middle ground , as such, could be much more than a compromise. But as I say I haven’t tried one yet.