The Prostars will be smaller/narrower; geared more towards tournament slalom skiing. The TriStars will be deeper/wider; geared more towards recreational skiing, pleasure boating.
If you park an old Tristar and a new MariStar 210,230/X-10,X-30 next to each other, the hulls look very, very similar. I believe the old TriStar hulls are almost identicle to the current MC's listed above.
While the older ProStars can put out a good wake, I would go with a TriStar.
I've got an 87 tristar 220 and love it. Very large boat, lots of space for weight, I've made a few changes to mine, put in a ballast system, pp etc. It puts out an awesome wake w/ people or weight. It doesn't corner very well like some smaller boats, but is a rocket in a straight line. I guess its about what you're looking to get out of it. If price is similar, I'd go with the larger boat.
Here the skinny on the tristar. I have a 190 closed bow and love it. You will have to add a fair amount of weight to get a good wake out of it. I run 1600 lbs in the back and 170 pushed as far forward as possible in the nose. I use sandbags in the nose and hold them in the front with a tie down strap hooked to the lift bolt that runs through it. You don't need as much in the nose on this boat cause the gas tank is in the nose. In the back I have 2 fat sacs that lay next to the engine pushed to the back then 3 sand bags under them and lead in the sides. The boat gets a little cramped with this much stuff in it. You will definetly need a tower and racks. A four blade prop will be a must as well. Once you get the boat set up like this you will love it. I like my wake just as good or better than my friends 2000 malibu sunsetter and my other friends 2001 moomba mob V. Which both of those boat we run around 2000 lbs plus people in. The tristar is great with holding speed. I can pretty much set the throttle and let go of it and it will hold a constanst speed. The down side is with all that weight it sits low in the water and water will have a tendancy to come over the back when you stop and over the nose if you aren't careful. Once you get the hang of driving it you shouldn't have a problem. I cant comment on the prostar cause I have never ridden behind one. Here are some pics of the wake. I ride at 24 mph and 80 feet.