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.
Somebody said they're getting 20+ Mh/s on the 4GB card, I'll be getting one to find out if that's the case.
In any case MSI has taken back their $350 a pop twin garbage cards and I'm stuck without cards or cash and a broken promise that they would call me in "two weeks"; this sucks almost as much as asic pre-order scams. These cards hurt less at $150 a pop if I'm going to get screwed like that on them.