I am a Nautique Promo Team member, so please know that I realize I am biased.
However, I have an 11 year old competitive slalom skier and have spent a lot of time driving and watching skiers at slower speeds and longer line lengths the last 4 years. Here are my observations:
1) Nautique: The Nautique 200 performs really well at slower speeds and has a small wake with the hydrogate deployed at all speeds. The boat is the best tracking boat of the lot. It is not super sensitive to balance, though I am pretty anal about this. The new SN is very comparable to the 200. The wake is slightly different, but it is still pretty flat at all speeds. One advantage of the Nautique is that it is a superior trick boat to the ProStar. Between the hydrogate and the new ballast system, it makes a very nice trick wake. At tournaments, very few skiers choose the ProStar for trick.
2) Mastercraft: The Mastercraft has always felt very similar to the Nautique in terms of wake. All of the B1 and B2 skiers seem to post similar scores behind these two boats in slalom. At 34, I don't have any complaints about the wake on the Prostar, but have always felt the pull was a little softer - I probably should play with my ZO setting for the ProStar, but haven't done so yet.
3) Malibu: The Malibu is fine for 34 mph - I usually ski about the same behind it as other boats. However, the slower speeds are very tough. Comparing tournament scores behind the Malibu with other boats for the B1 kids there was consistently 4-6 balls difference in scores. This was really discouraging for the kids and several of them developed an attitude about the boat. There are different schools of thought here, but generally I lean towards trying to help my son enjoy practice and competing as much as possible and having this boat on our dock would be a deterrent from practicing. It is a solid trick boat and plenty of people choose it for the trick event at tournaments.
As others have said, go test them and the relationship with your local dealer should be a major consideration.
Thanks,
Dan