Badly need help with blue/white mtg deck?

Im running a Blue/White deck. Alot of Blue counters and mostly white flyers and enchants. Im looking for good blue creature spell to add in. I was looking at adding 4 Conundrum Sphinx but i have no way to scry in my deck for its special ability. It is still a 4/4 flyer for only 4 mana. Or i was thinking about adding 4 Phantom Warriors a 2/2 creature that is unblockable and 3 mana cost instead. If you have any better suggestions or can help me choose it would be most appreciated.