Well I have both.
JK is exceptional on the street compared to my TJ. (Keep in mind my TJ is running 33' MTR's) so that would be part of the issue there.
JK comes with stronger axles assuming you don't get the base X, but you can get the 44 in the X.
For trails: I really like the smallness of my TJ on the trails in Coloardo. However, I think the JK would be a better platform to modify for an area like Moab.
While it is fairly cheap to stuff 35's on a JK. The aftermarket is quite expensive for bumpers and armor.
Those are just thoughts, I think both have their pluses.
So in the end if you are thinking about a vehicle which will be driven primarily as a DD, I would go with the JK.
If this is going to be a trail toy, I would go with the Unlimited LJ used or keep your TJ.
2010 2dr Rubicon - Mango Tango!
Colorado Jeep Club Member #11
2002 TJ Sahara, 2007 JK Unlimited Sahara, 2004 WJ & 1986 CJ-7