I’ve got both a 29er (a custom set of bits on a nimbus II frame) and a coker.
If there are no space constraints and you don’t want to take it on public transport regularly, for all out road riding, I’d get a coker. If you ride regularly, you’ll be able to control it just fine. I’ve got 110 cranks on mine and I can still stop quickly, idle, do tight turns etc.
29ers are cool for several things.
Firstly if you’re not riding regularly, or using it for transport, a coker can be a bit hard to control. If that’s so, a 29er may be more you. Having said that, cokers are rather addictive, so you may ride it more than you’d expect. I found myself commuting daily to work on mine very soon after I bought it.
Secondly, if you want to ride a combination of offroad and on road, a 29er is great fun. Not as hardcore as a 26 or 24, but a 29er with 125s is fantastic for riding fast down singletrack and rides really nice over roots and things like that. With a brake and 125s, you’ve got a really flexible machine that you can hit pretty much any riding that doesn’t have big drops on, yet ride at almost bike speeds, and still have decent speed for getting to the trails or riding road sections between trails. Having a wide rim like the KH one really makes a difference if you’re running a 29er tyre, as with a narrower rim you get problems with the tyre folding over. I’m not sure what the Yuni rim is though, I think it might be quite wide.
Thirdly, 29ers are so easy to transport, just pop the wheel in a standard wheel bag and it’s just another piece of luggage.
Fourthly, you have a good choice of tyres, so you can tune them more, from the mini-coker Big Apple, to narrow road racing tyres, to some okay muni tyres.
Speed wise, as always it’s more about the rider than the bike. If you ride a lot, you can go quite fast on a 29er with 125s. I could keep up fine with coker riders when I was riding a 29er all the time, but I was riding 20 miles a day for a couple of years, which kept me rather fit. Not being able to put shorter cranks than 125s on the KH29er may be bad if you want an all out speed and distance machine, but in that case I’d just get a coker.
Where the coker really comes into it’s own isn’t so much speed, it’s distance. For a 30 mile ride, I’d be happy on my 29er or coker. I wouldn’t do a 50 to 100 miler on a 29er if there was any possibility I could use the coker, it’s way more relaxing to ride.