This is easy. Do NOT buy the DI skis. Bottom line, when they are running as they should they are fantastic skis. When they need repair, they are harder and MUCH more expensive to fix. We have help so many with the DI skis that we can normally figure the issue out pretty quick, but it will cost you more money and some special tools. For example, the fuel pump, which is a common failure, cost several hundreds of dollars.
The RXT-X and RXP are basically the same ski. The P is a two seater and the T is a three seater. I own two skis, one is a 209 RXT with the 255 engine. I can not stress enough of much I enjoy the ski.If it were me, I would buy the RXT as it is a bit larger, you can carry three people which means you can tow a tube or a skier legally. Now that I have re-read your post, I see you will buy both the T and P ski. Without a doubt that is what I would do.
You do need to know about the Super Chargers though. Until l200 they had ceramic washers in them. These washers fail and the parts fall into the engine. If you are lucky and catch this, you still have to pull the engine to do a major cleaning and removing of all the ceramic parts as the will harm the engine. If you don't catch it, you will be spending money in the form of engine repair. If the present owner says, "They were rebuilt in 2009 ect ect ect" It means NOTHING unless he can provide proof os the rebuild. Further, they are slated to be rebuilt ever 100 hours. Once they are rebuilt with the update kit, then they can go for 200 hours. Are the Super Chargers more of an expense? Yes, but the performance you get from them will put a smile on your face every time you ride it.