I think if you consider the reverse of these ponderings you can see the benefit of 29ers if you’re tall:
“…we got a couple of 16” [Solaris] frames with top tubes 10mm shorter than the medium (it’s the shortest we could go whilst maintaining fork adjuster clearance). Paul was our test rider as he’s 5ft 8in and runs a small Soul.
The most surprising thing was that with flat bars we were able to replicate Paul’s Soul position pretty easily even with the much longer top tube. However, this was using an inline seatpost rather than layback, and a 60mm stem as opposed to 65mm on the Soul. Paul’s done a good few rides on the bike now. Basically it’s extremely fast rolling and secure – as you’d expect – but Paul can’t really move the bike around. Due to the low BB, larger BB/head tube distance and longer back end, he hasn’t got long enough arms and legs to throw his weight outside the wheels. This is compounded by the 29er having a much lower BB relative to the axles than a 26″ bike. Seeing him ride, he’s almost trapped between the wheels. We’ve went down to a 50mm stem to push him back a bit on the bike to try and counter this and it helped a bit, but it also made the steering too light and quick.
It’s interesting, because Paul’s a really talented and able rider, with a trials background, so he can and does move a bike around a lot when riding. He just can’t with the 29er, so he doesn’t like it. It’s not as much fun as the 26″ bike. The interesting thing is that once people are this kind of height, the 29″ almost seem to define the use of the bike as something quite different to a 26″ bike. If Paul wanted a light, comfortable, efficient thing for crossing a map, then the 29er would be good. For having fun and generally enjoying riding bikes, you won’t be that surprised to hear he’s back on his Soul. This is in total contrast to Cy, who at 6ft 3in didn’t feel he needed to adapt much at all to the 29er, but he has long enough levers to get his weight moving outside the wheels.”
A larger wheel will roll and grip better offroad but if it’s too large compared to the rider then you’ll struggle to make it handle direction changes well. The bigger the rider, the more leverage and mass you have available to control the bike so you can take advantage of bigger wheels. FWIW I’m 5’10.5″ and am perfectly happy on a Soul, I’m no 29er fanatic.