For me, I would go Connor because of the situation he will find himself in with the Peg. Great situation when you look at Laine, Schiefele, Wheeler, Ehlers, Buff. He is a good enough player to put up good production, but with those guys around, it's guaranteed!
Rantanen and not that far behind Connor, same thing, going into a great situation with the cast members in Colorado. He will succeed there.
Vesey, depends on where he decides to sign. He is a player I feel depends on good line mates for his production and isn't as capable as the other two to do it himself, he won't drive the scoring. Plus I have an issue with these guys coming out of college and using the four year rule(see Schultz, Hayes etc.). Rarely have these types been worth the reach, they are gambles.
Go with your gut, but this is how I see them!