I too think your question is loaded... Are we talking about running bigger tires in the mud or snow? Then bigger tires will get you farther than smaller ones no matter what your RTI is. Rock crawling? I'd probably go with better RTI over tires with 1" more clearance.
RTI does count for something, at least at the extremes, as it is a measure of the vehicle's ability to flex and accomodate obstacles without lifting tires. If you're in a vehicle with really poor flex, you're lifting tires all the time, and a tire in the air is one less tire making traction. Given two otherwise identical vehicles, the one with better flex will obviously do better offroad...
Want to look cooler while offroad? DEFINITELY go with the bigger tire and less flex. Lifting tires makes the trail look hard and makes for cool photos.
I built my TJ for Moab originally, before the damn side by sides and rock buggies tore it all to hell. My buddies all had YJ's. We all did the same trails, but they had tires in the air all the time. I don't recall ever managing to even lift a tire hardly. Same line, same obstacle, their pics are "cool", mine look lame. For the most part, we all went the same places though. I just made it look easy, and with less pucker factor. And smaller tires...
FWIW, I found that my tires rubbed hard enough on the front fenders at full stuff to bend the inner lip, especially if I was turning. Instead of limiting travel, I chose to keep my travel and put a 3/4" body lift on the Jeep, along with a 1" motor mount lift. Now I have no rubbing, 1" more clearance under the oil pan, and very nice suspension geometry. Perhaps you can think outside the box and get 35's to fit without limiting up-travel... ??