First of all, wow, they really knocked back the price on that huni-rex. At that price they just might be worth trying out. OK over to the 2008 KH29
Looking at the unicycle in question I am not convinced it really is a 2008 KH29, more likely a 2008 KH29 frame with a mixture of newer parts.
It doesn’t say in the description but in the picture it looks like the 2009 saddle and 2011 seatpost. The pre 2009 freeride saddle is good but the 2009+ one is better, it’s worth throwing them an e-mial to clarify what you would get if you order the unicycle. The rest looks 2008 to me.
There are minor differences in the hub and rim but no major change to the current model.
The Moment cranks on the 2008 are heavier than the current Spirit cranks. Both crank styles are pretty bomb-proof and if you aren’t using a disk brake I would be perfectly happy with the dual hole Moments.
I haven’t ridden either of those tires so I can’t comment on which is better.
The KH is more of an off-road 29er though so not really that comparable to a Huni-rex. If you wanted a road setup it might make sense to go with a cheeper Nimbus, but they aren’t on sale and I have gone on tangents of want like this before, I know what you are going through.
This unicycle with it’s current specification was released in 2008. Between 2008 and 2012 when the disc verisons where released the components changed. Seatpost slightly changed, along with the saddle covers. Pedals became plastic. Basically when this unicycle was replaced in 2012 it came with lots of “2011” bits… But with the model is still technically 2008 so we have to sell it as the 2008. To the well trained eye its a bit of a bargain. Hope this helps.