Weird size question
 

I am in the market for a new MTB. Heavy into road cycling but going for a new MTB. Getting a specialized rockhopper. Cant decide first of all on a traditional 26er, or a 29er? Next, I own a Specialiszed cross trail in a 19". It is a bit too big for me. I have a weird body apparently. I am 6' but have a longer torso and shorter legs. On a road bike, everyone when I tell them I am 6' says on you are a 598cm bike without actually measuring me. Once inseam etc are measured I come out to a 56.2cm bike in a perfect world. So, according to everyone I should be a 19" MTB, however I am debating a 17.5". Also the 29er in a 19" is bigger than a 26er in a 19" and then also the 17.5 in a 29er is bigger than a 26er in a 17.5. Am I crazy for thinking that if I get a 29er I should go with the 17.5 but maybe if I go with the 26er go with the 19? Make any sense? Any BTW please do not respond with, go test ride the bikes and see what feels best. I am looking for opinions etc. Anyone else out there in my position? Anyone out there around 6' ride a 17.5 or should I absolutely be a 19"?

One of my opinions is that you get the smallest possible frame that you feel comfortable on. It'll be lighter, stiffer, more maneuverable, and give you more standover clearance.

Another one of my opinions is that you shouldn't try to apply what you know about road bike sizing and rider positioning to mtbs.

And finally, it is my opinion that opinions are worthless unless you actually test ride the bikes and see what feels best.

I'm in a similar situation with more body than legs. (6'3", 33" inseam) I'm kinda thinking that the 29er will have a longer top tube to accommodate the slightly larger wheels, that might help.

What Crypt says is hard to top and fits my thinking. Lighter means less work, smaller means nimble. Comfort means you will want to ride more. Stems and seat adjustment can make up for the tops tube length and get your body in good position.

What is your primary riding interest? XC, downhill, racing, camping, recreational sightseeing?

probably be doing a lot of light tray riding with some occasional single track and lots of recreational riding. also will ride it on the road with my kids when they wanna go for a bike ride

More rougher harder riding would mean get the smaller stronger more nimble wheels. Having said that the 29er will be OK at it too - a friend just bought a light 29er - he's very hard to keep up with on smooth trails now.