I think it depends on the type of 4 wheeling you do. I think deep snow vs rock crawling would be the 2 extremes. I will give the snow example, but I have no rock experience, just a theory.
Snow (and deep sand hill climbs) sometimes requires alot of speed and heavy throttle. That's why you see alot of jeeps in the mid west converted to V8s. When you are trying to turn when really thrashing on the throttle, you can feel the steering wheel pulling back and forth in your hands. I believe that's because u-joints speed up and slow down 2 times per revolution ( that's why a driveshaft without a double cardan at the tcase needs equal angles at both ends. They cancel each other out). So, the between the spline of the axle shaft and the tire you have this u joint wanting to go straight, but it cant because you are forcing it to run at an angle with the steering wheel. You can see the front wheels moving back and forth if the jeep is coming at you. This is when I see u joints break. This is when I think RCVs would shine. A ball and cage cv joint transfers power much smoother than a u joint. It's why grand cherokees with full time cases had CVs in the front axle( they are not really strong enough for bigger tires, too bad)
I think in rock crawling ( no experience, just theory) the speeds are much slower and throttle application is much more controlled. You probably would not have the steering at full lock and apply full power if you could help it. Maybe a u joint is better ( or equal) in these situations.
From what I have seen, the stock size u joints are strong enough. I think bigger (stronger ) u joints will possibly just transfer the break to the ring and pinion. No thanks. Axle shaft can be swapped out in minutes. I pulled a Dana 44 carrier out on the trail once because of a shrapnelled ring and pinion in 20 degrees and snow. That sucked, but led to good stories later in the garage over a couple of beers.
I know this got drug out a bit (kind of
rambled on), my opinion:
Snow/sand= RCV would be cool
Rocks=u joints ok?
Oversize u joints= transfers the problem to something else.
One last thing. Full circle snap rings help keep the caps on the u joint much better. That helps prevent the cap from ejecting out of the axle shaft.
