Seth, Ive had multiple variations of both. First let me say you can not go wrong with EITHER.
Speed wise lets just compare glass to glass, in that comparison they are very close. The Centaur may be a touch faster, but again so close its a toss up (again this is glass/glass, if you consider the Chimera or Carbon Elite, its the Centaur for "speed").
While both quiet, the WHIP is the quietest bow ive ever shot. This isn't a knock on the Centaur as its also quiet, but I have no idea how Dan gets that Whip so darn silent.
Fit/Finish is also a toss up. The Centaur has a flat almost textured finish, the Whip has flat but smoother finish. Both do the job in protecting the bow and giving you a non glare finish. Both bowyers get really nice wood and know how to put combos together.
The Centaur can be had in shorter lengths for the same draw length. My 62" Whip feels about the same as the 60" Centaur for smoothness etc.
I prefer the grip on the Centaur, really like the contouring and way Jim peaks/contours the shelf.
You can get the Whip in "classic" trim which is a leather covered/simpler grip, or the standard which has a bit more contour and thumb rest.
The Whip has very fine, small tips, the Centaur tips, while also sleek are a bit more robust.
So im sure that wasn't much help! Just my view in the differences between the bows. For me its that Centaur grip that pushes it to the head of the pack of all hybrid longbows.
They are BOTH fantastic all around bows that are at the top of the hill.