I did a lot of back-to-back testing of my Soul vs Solaris prototype on repetitive loops to get my head around exactly this subject. Basically both wheel sizes have their advantages, and it's possible to design a 29er these days that is great all round, so it's a preference thing. The two massively obvious things I found were:
- On certain size bumps (DH run with lots of 2 fist size roundish boulders) that are just big enough and widely enough spaced to batter 26" wheels, the 29er flew down at nearly FS speeds. It was quite shocking. That said, the Soul was reall fun, popping over sections and from rock to rock, just not as fast. 29er was way faster, but not as interactive as the BB drop seemed to make it harder to move around. The thing was, I didn't need to move it around.
- Tight, steep, technical DH or climbs, the Soul is better simply because you can make tighter turns and there's less bike around you.
- 29ers are super-naturally good across roots. You end up riding across them with impunety just because you can.
- On fast sweeping singletrack, there's not a lot to choose.
- Spec-for-spec, my Soul is about 3/4lb lighter than my 29er.
I think the major issue here is bike fit and weight distribution. I'm ft 3in and even with a 110mm head tube on the first prototype I struggled to get the bars low enough for my liking, and even with 15mm risers I couldn't get the front 'switched on'. Flat bars were the only option, and granted I do like a low front for my height, but if I struggled then the bike fit and handling issues for shorter people are very real. This is why we're not doing a small size to start with. Although we're going to try out a small to see if we can make it work as there's demand, the way I see things right now, if you're under 5ft 10in, then stick with 26" wheels. You'll be able to ride the thing proprly.
, but I don't expect or care particularly if anybody else does/doesn't. I'm not pushing them or asking anyone to buy one, but am happy to let 29er curious mates a have go 
