@Cash-Rewards First of all, how dare you call an 07 'old'
I'm not too familiar with the JK generation. I know it was the first Daimler-designed Wrangler. The 3.6 is a weak motor but I've heard they're pretty solid and have a strong aftermarket.
2006, the last year of the TJ, was also the last year of the venerable AMC/Chrysler engines. The 2.5 I-4 was gutless but strong. The 4.0 I-6 was slightly less gutless and also stronk. Unfortunately many of them these days are either high miles, pristine, and expensive, or super high miles, basket-cases, and still too much money. Regardless they're pretty simple to work on, easy to keep running, and you just know they will continue running until the frame rots away. IMO one of the best Wrangler generations is the TJ (not biased)
One more thing to note: they're all pretty much terrible to drive on the road. The JL is by far the most comfortable, but it's still a brick with wagon suspension and it will fight the atmosphere at highway speeds.