I've had both.
1997 Four Winns 27' with twin Volvo throttle-body injected 4.3's. NOT a duo-prop.
1992 Carver 26 Flybridge with twin Merc carbed (4 barrel) 4.3's.
In some respects I'm comparing apples to oranges, but I think that the major differences between the two boats kinda even out, i.e., the Carver is 1,000 lbs heavier than the Four Winns, but has less deadrise. 15 degrees vs.18 for the FW.
Starting was a little easier with EFI. Performance 'out of the hole' is similar. The Four Winns could run up to 36-37 mph. The Carver has hit 39+. The big difference is in economy. I never had a fuel flow meter, but over a couple of seasons of similar use the Four Winns averaged 1.6 mpg, where the Carver does 1.2.
A boat with MPI would likely do better than either of them.
My .02