I spent a fair amount of time and research looking at this class of boat. Both of these choices are fantastic boats. We saw both of them as well as the Super Air Nautiques, MB, Moomba, and Tige at the Denver Boat Show. Personally, I like the interior of the Malibu a little better, and at least here, it seemed like the Malibu was a LITTLE less expensive than the Mastercraft if similarly equipped - but that will be dependent on what you put on them. Malibu also has come out with the 21 VLX, which is a value priced boat (standard price of $79,995 pretty well equipped). If you can take on a 21' boat, I would take a look at it too. I thought Tige had some nice offerings in this space too. Narrow your choices down, and get the dealers to take you out. It is the best research you can do.
In the end my decision came down to a Malibu 20 VTX, and the 22 VLX. The 20 VTX is the king of the crossovers for Malibu. It has a GREAT reputation as a crossover. It has a center ski pylon available, great for slalom. It also has the surfgate, and power wedge that you find on all the Malibu's that make killer wakeboard and surf waves. I REALLY liked it a lot. But when I compared it to the 22 VLX, the 22 felt proportionally a LOT bigger (due in part to the wider beam - 98" vs 102"). The cabin is a little deeper too. In the end, it won out because of the extra space as we expect to routinely have a crew of 6-8. The bigger boat will not put out as soft or flat slalom wake, but I was willing to trade that for space (I am an older recreational slalom skier). I don't know about the Mastercraft, but with Malibu you can get either the Diamond hull (multisport), or the WakePlus hull which is optimized for wake sports.
There is a LOT more in the decision, would be happy to share more if you are interested, but in the name of brevity, Ill just add that SkiDad nailed it. We bought a '97 Crownline 182BR in 2014. I spent less than 10K on it, and it was very low hours, and METICULOUSLY maintained (yep, you CAN find boats like that if you look). We had a BLAST with it. It proved to me that I really was serious about boating before I spent bigger money. Craigslist is littered with wake boats that people bought into new, ate the depreciation, then found that they didn't use them enough and wind up selling them and taking a huge financial hit. I am not trying to talk you out of a great boat (you would love either I think), but it really did take me 2 and a half seasons to know that we would use a boat like this enough to make it worth it (we floated the boat 30 times last season - pretty much all we did last summer). Now I am heading into semi retirement, and expect to be able to get out even more.
EDIT>>> just read your thread over at ballofspray... good stuff. Sounds like you are a more accomplished slalom skier than I am - so my opinion on the wake is probably not valid. I am looking to transition more and more to surfing over the next 5 years, so I am willing to tolerate a little larger wake in the name of multisport. Also sounds like you are already there for a NEWER boat at least... fun stuff. Think I had as much fun in the search as I will have when I launch this spring!
Whatever you do, best of luck with your decision... Fun times ahead!