I had a TriStar with tandem trailer, traded it for ProStar 205 with single axle trailer. I still have a 1991 Ski Pro with tandem trailer.
I use both boats, albeit for different purposes. I will NOT give up the ProStar; it's a fabulous ski boat. But he truth is, the Ski Pro is better in most other ways: It's quieter, faster, rides better, has more room, has a built-in boom, will back up in both directions, etc.
The original plan was to sell the Ski Pro, as we thought the 205 should cover all the bases. Now we're waffling on that.
Re single axle v double axle: I can tell the difference, but it doesn't bother me. I like the ride a tandem offers, but I like the maneuverability and simplicity the single axle offers. I wouldn't make it a selling point unless you haul your boat thousands of miles a year. Your boat won't care what it's sitting on.
Since you're a recreational skier and have a growing family, the MariStar is probably more practical. Your kids will want to go boarding/surfing and bring their friends, and it will do a better job.