Last night my chest injury had finally eased off enough to attempt a couple of my standard muni rides up on the local hills on my 29er (I’ve done most of my muni riding on a 26er). Was amazed at how much faster I was - averaged over 11km/h for both rides, when I don’t think I’ve ever broken 10km/h on the 26er. Admittedly the trails are the driest I’ve seen them since I’ve been riding muni, and certainly riding a lot faster than they have done when I’ve ridden them on a 26er, but that’s still a much larger difference than I was expecting. I suppose I’m also fitter than I’ve been since my technique was a lot worse. I did still manage to ride all but one of the climbs I normally manage (the one I failed on I had just ridden further up the previous climb than I ever had before), including riding one section of climbs I rarely clean on the 26er.
I’ll have to go back out and ride them on the 26er whilst they’re in their current condition and with my current fitness to see what the real difference, but I suspect I’ve just spoilt them for 26er riding as it will just feel slow. Most significantly that average speed is now faster than I could run the same trails - before I’d always considered that I was faster running than muni.
You’ll likely find that easy trails are more fun on the 29er; the extra speed and flow makes everything better. But the 26 is still more fun on difficult trails; you just need to go find trails which are too hard to ride on the 29er.
Most of the stuff round me is doable on my 29 (2.1" tyre, 140 cranks) but the rockier stuff I still find faster on the 26 (3" with 150s) because the big tyre means you can be less careful. 29 (or 36) is nicer on the easier stuff though.
I definitely have a use for both sizes, depending on route and mood.
As for the running comparison, I reckon a good runner could keep up with me on most of my local trails, but I’m definitely faster on a muni than I could run over any more than a couple of hundred yards (I don’t do running!). There used to be a keen runner I’d see quite often on my xc route home from work and we were pretty evenly matched for speed (and the rougher the trail the more it went in the runner’s favour).
That’s the biggest difference for me at the moment - quite happy to hop a 26er around, less so the 29er. I’m sure the 29er will get easier with experience though - not like there should be a huge difference, much less than between a 20 and a 26, and I remember when I wasn’t happy hopping the 26. Mind you I don’t normally do all that much hopping on my muni rides anyway - generally only to get around tight corners.
Actually, for a lot of Slickrock, a 36er with a brake and long cranks is pretty good. It’s definitely better than a 24" on the flat sections, more flowy. On the downs it’s very scary, but doable with a good brake. On the ups it’s a lot of walking, but for most people that’s what they do on the ups on Slickrock anyway.
Slickrock isn’t really technical, it’s steep ups and downs with infinite traction.