Green's creatures are, on average, the largest
and strongest in combat, which doesn't always
matter when blue's creatures get tricky.
Fortunately, somebody seems to have realized
this (not Mark Rosewater perhaps, but that's a
discussion for a different time), and Duskwatch
Recruiter can be as effective as Azure Mage in
the right settings. When your creatures are the
strongest on average and you also have a steady
stream of them coming, you're in pretty good
shape; the fact that the "day" side's
card-drawing ability doesn't affect werewolf
flipping is also sometimes relevant.