I have both and while I love my CJ-7. I would lean more towards a TJ unless you can find a CJ in great condition I.E. no rust or puddy and perfect engine(rebuilt or swapped).
Alot of the CJ's you find cheap will need body work or frame work done due to rust and the engines are probably going to have high mileage. This can mean rear seals leaking oil, valve jobs, new tranny and tranfer case,etc. plus you have to deal with the problem caused by the carter carb which you should replace with a good weber carb or other brand.
A TJ shouldn't have much rust if any since they have only been around for close to 10 years. Plus you get fuel injection, and if you get a 2000 or up you get a coil rail instead of distributor which is a plus if going through mud or any water crossing( not saying to swamp your jeep) which is nice when you make it through and the other guy is sitting in the middle with his hood up waiting for the distributor to dry and is impressed by your jeep and ask for a tow out plus gives you bragging rights

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So you may save some money by buyin a CJ but you might end up paying more on fixing it up than if you bought a TJ.