Im not entirely sure why they are cheaper, maybe they arent as desirable in your area? I just bought a 04 with the 4.0 and 242. Ive had a 2000 with the 4.7 and it was the biggest headache ive ever had. Had good power, but that was all that was good about it. The first one lasted 213k miles and then the rebuild lasted 10k, it was covered under warranty so we got it rebuilt again and it blew up 15k later. Stay away from the 4.7. The quadradrive was a good TC, never had any issues with it, but i personally like the option of 2wd. So when I was looking for my next wj, I made sure of the 4.0. Almost all problems I had were in connection to the Limited 4.7 models. The heater core for dual climate control is something that goes out on almost every WJ around 100k miles (where it blows cold out one side and hot out the other, and its a huge PITA to fix). Also my D44A was howling at 200k miles. Not sure from what but it just didnt last. I bet a D35 would have lasted longer. But the 44a is something that comes with the 4.7.
Anyways, if your looking around.. Id recommend a WJ over a cherokee, and look for the 4.0. The newer the year the better IMO