+Ed C I think your question helps illuminate the answer some. I don't know that we have a clear answer. Golf has always been tricky that way. Many different body types meet the requirements. It's not like football where you won't see a tiny lineman or a really large wide receiver. There is a relationship with strength and power. You don't see too many long drive competitors who are really small and wiry.
Also keep in mind that you have 3 different basic body shapes (morphotypes). Ectomorph, Endomorph, Mesomorph. Dustin, Brooks, and Gary Woodland look different partly because of their body morphotype. Bryson appears to be more of a Mesomorph, and they can put on muscle pretty easily. Dustin would probably have a harder time bulking up like that, but could still possibly benefit from strength training.
Simple answer, we don't have enough info to say that one is better for longevity. I'm a big fan of muscle to help protect joints, but you also have to maintain quality of motion and a range of motion to excel at golf.
Distance seems to be more and more important, so we will probably see more larger muscular golfer trying to get that 190 ball speed. ;)