The yellow XP is a one person machine. Its next to impossible to even board it with two people. The white one will hold two.
Almost a rule: A 2 person PWC is really only comfy with 1; a 3 person PWC is really only comfy with 2, and so on. You can take the max rated on the ski for quick blasts, but that's about it. Remember everyone is holding onto the driver, and it tires you fast.
There are five million opinions on this, but I would not buy a Sea-Doo that needs work. Sea-Doo can make a nice PWC, but the Rotax system has many quirks, and is just not intuitive to figure out. I'd go with a Yamaha; 800+ cc.