Davis is the clear-cut #1 prospect. The kid's ceiling is limitless. He's still raw, though, as a prospect, but he'll be at worst a Marcus Camby-type player and possibly (and likely) much better offensively with his skill set.
MKG would be #2 on my list. Great all-around game and he's a terrific defender.
Beal would be #3. Great offensive player. I'm a bit worried about his size, as he might be shorter than the listed 6'4". Could be a Monta Ellis-type of player.
I think Barnes would be a good fit in Toronto. The club needs a shooter, and Barnes fits the bill.