Depending on what kind of off-roading you do, a YJ could be just as useful and, with a change in body style, 4500.00 would get you further.
Having both and getting just as far in one as the other, if you are a Do-It-Yourselfer, the YJ tends to be a little easier and usually less expensive where suspension mods are concerned.
TJ's are softer riding and seem to have more out-of-the-box/off-the-assy-line flex and ability, but you said you wern't hung up on the ride and, again, depending on what kind of off-road you do, flex may be sacrificable to you.
And, if it's a second vehicle, the somewhat-plain-I-think-more-Jeepier interior won't bother you at all.
And, with everything else to consider, I'm not going to tell you what I think of people that let headlight shape be a deciding factor.
You said you are looking for a 6cyl too...STICK WITH THAT! And try to go '91-'95 so you can get the 4.0ltr. I don't think I've heard anything that great about the older 4.2ltr. If you're looking to build, TRY to get a '95 for the larger U-joints, too.
You're gonna have to be real patient to find a dependable TJ for 4500.00, but it is doable.

Again, I've had both and, as much as I love my TJ, I also loved my YJ and, in the future, for something that I can build more, I'll be looking to a YJ.