Yeah, I'm kinda dangerous on stage no matter what bass I play. The P is the worst, since I play the 'Bird nearly vertical. That solves any neck dive problems and makes it insanely comfortable to play. For me, it is far more comfortable than a Fender, but I'm probably a freak.
I have had a bolt on 'Bird and now have a Pro IV. There are a whole lot of differences. The bolt on 'Bird neck is very large. It isn't just wide, it is deep, too. It is like a P neck only with some girth instead of a flattened out D-shape like Fender seems to think is a good idea these days. I really liked it. The pickups are better than they have a right to be. It is passive. The finish is so thick that you could probably toss it in the ocean, and it would be fine when it washed up if the barnicles didn't foul the strings too much. Overall, it's a decent bass once you sort out where the upper strap button is. The three point bridge is not my favorite.
The Pro IV is very different in most ways. Some are really obvious, like the fact that it is neck through. The bridge is much, much better. The neck is thin and feels almost delicate to me, although I don't think it is partciularly delicate. It has a good shape for its width and doesn't feel like a noodle or flattened out road kill. The frets are tall, which I don't especially like, and mine is de-fretted now anyway. The neck is a really good shape for de-fretting, at least to my hands. I hate the preamp. It can sound OK, but it is hard to get much besides a very modern, scooped sound. You can slap and pop with it just fine, once you get used to the idea that you are doing that on a 'Bird. It sounds very different from a bolt on for all of these reasons. They are both good and long, but that's what a 'Bird is all about anyway.
As far as finish, the Pro IV I have is burst just like the bolt on was, but the bolt on was practically black, while the Pro IV is a much more varied color and the finish looks a whole lot better. There are a couple of chips in the finish on my current 'Bird. Finish on the body is very thick, but the neck finish seems to be much thinner. If you like a matte finish, you can get a Pro IV with what I guess is a clear, matte finish. It feels much thinner than the high gloss burst finish.
Otherwise, they are identical.
