Depends on the kind of riding you do and the water conditions you ride in. I have an RXT-X 300 and my brother has an RXP-X 300. Both are rocket ships. The PX gives you turning ability second to none. Its a " lean in" turn ride, you can really hang it over on its side and it will hook up. It will turn harder than you can hold on. Really shines on a buoy course. Also, It's only 9 inches shorter than my TX so it's not that noticeably shorter than the TX.
The TX is a stepped hull. It CRUSHES rough water and still has the ability to turn tight, thanks to the ergo-lock seat setup. I ran a buoy race last week and was really impressed with how well it does on a tight course. The TX also has the adjustable riser so you can pull the handlebars up if you like to stand. A lot more storage on the TX too. I disagree with not being able to jump the TX. I absolutely launch this thing off a decent wave/wake.
The 300 power plant is a savage. It works great in both machines. The TX is actually a tick faster than the PX due to the stepped hull on the TX.
If you plan on spending your days carving extreme G force turns in good water, and razor sharp handling in chop, then the PX is your ride. If you plan on riding in rough water conditions with the ability to hammer sharp turns on a bigger boat, with a little more adjustability and storage, then the TX is for you. Honestly, you can't go wrong with either. I like em both. The TX was a tad bit more appealing to me. For my brother, it was the PX.