Yep, get both...

My opinion: P3P is more interesting to fly. P4 is somewhat boring if you want to take advantage of the sense and avoid/stop feature.(if you disable it you get a P3P I guess, for more money.)
P3P is very stable, but P4 is static! (once it stops its yoyo - didn't upgrade yet , dont know if it is solved) P4 has a better look, better finish. Better engines, batteries are more modern, better/easier connectors.
P3P is way cheaper.P3 Video is really good. P4 Video is really really good.
I was happy with the P3, but crashed it (my fault) and did need one for a job. So I got the P4 because it was the new one but to be honest, I think the P3P is absolutely fine. Now that my P3 is back from repair, I have a P4 as main, and the p3 as backup. My conclusion: Get a P3P, but that's just me.