What I've noticed is that TJs with open diffs, just due to the greater flex, can just about match an SUA YJ with a rear locker.  It may sound like I'm exaggerating but I've seen it happen on several trips on rocks (also see the Bash videos that I think Art posted one time).  With really low pressure, the tire provides extra effective flex about equivalent to the sidewall height (about 9" with a 33" tire).  Just estimating, this might be enough to bring a YJ close to TJ flex. I may be wrong but I've come to believe in the awesome power of flex and low tire pressure!