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!
Its ok to love your tj more than a yj but I have to call bs on this one. I have put my yj in places my tj friends wouldnt go because I am a bit more stable. Also everybody takes a different line I have seen inexperienced jeeps go over stuff the exp jeeper couldnt and vice versa. I have seen some open jeeps go whip thru some stuff that a locked jeep had problems. I am locked in front with lsd(8.8)in rear and theres no way I am trading my yj for an open tj. I have seen and pulled thru countless coil sprung jeeps where the flex and the line they chose caused them to spin a tire or 2. The further an axle is stuffed in one side the higher the chance the droop side is going to loose traction exp in an open rig.
I agree that low tire pressure has no substitute in certain if not all situations giving the tire the abililty to wrap around a root/rock/rutt. This isnt due to flex however its due to increasing the surface area thats making contact.
I went with the gy mtr mostly because of the tougher side walls and the fact I will be airing down further now that I have bead locks.
No 2 rigs are exactly alike and no one rig is hands down the better rig in all situations. The only thing that matters is that you are out there enjoying your rig picking lines and having fun.