Well shall I put it this way. Would you do ragbrai on a coker or on a 29"?
use the 29"
unless you want to make good time
Long ride? Definitely Coker. No question. Especially if most of your fellow riders will be on bikes!
Today Jess Riegel and I rode 15 miles of dirt on our Cokers. We walked up some of the hills (125s for me and 150s for him), but we also rode up plenty. It was a really fun ride and we hope to do more (except he’s going back to school next week!).
Coker. No question.
Jagur posted some good anti-Coker points in the other thread. Hopefully you can get some more anti-Coker, pro-29er opinions but Jagur is the most outspoken and his reasons are well thought out and come from experience.
I’ve become a sucker for the ‘coker’, but you can still do whatever you put you mind to with a 29". It may not be quite as fast unless you are really keen at spinning, but there’s nothing to stop you from doing long rides. My second longest one-day ride ever was before I had my 36er - 103 miles on roads, on a standard Nimbus 29" with 125s. Also a two days of 75 miles back to back, which left me feeling ok. It seems a little silly now I know how nice a 36" wheel feels, but it can be done. Most 29ers will be very noticably lighter than any 36er you’ll ride.
If you already have a 29", and are happy with it, just go with it. If you need the excuse to convince yourself to go all the way up to the 36", it might be a good excuse. Riding with bikes is generally easier with a 36", but is still a push unless bikes are slowish or want to ride with you. I used my UK End to End tour as my excuse, and ever since have been glad I did. 
Sorry, that wasn’t very anti-coker I’m afraid.
Sam