Yeah, I pretty much know I need a 5. My wife wouldn't let me bring another 4 into the house anyway as she knows I always sell them.
A P may work for you. If I could only have one bass, it would be my Jazz. As far as 4 vs. 5, I started on a 5 and now exclusively play 4 strings. Playing a 4 makes me a completely different player. I may pickup a 5er again as they do make things a bit easier, but a 4 banger is just fun.