Read up on, and demo both boats. I would expect a similarly equipped MC to command a higher price than a Supra, all things equal. The engine upgrade is another factor coming into play.
Is it likely that the MC will sell for $6,000 more? Very possibly. Is it worth $6,000 more to you? That's another question...
I will say a competitively priced late model X-9 can be a good value, multi-purpose boat, but the Launch has gotten raves for its wake when loaded down.
Comparison shop on
www.boattraderonline.com and
www.flipsell.com. There are good deals out there...