Apparently there is no RX470, AMD went from 460 to 480. The 470 is just an overclocked 460 with 4GB that the mfg's decided to call a 470. They (the mfg's) had no reference design, stuffed in ram they found in a recycling bin and pawned them off on unsuspecting consumers.
That being said, I'll be getting some rx460's with 4GB samsung ram later this week for half the cost of a 480.
Good luck with Your purchase. Of course they are the same if You omit fact that You need two RX460 to match one RX470/480 hashrate.