If getting 480 make sure its an 8gb. It has quite a bit less shaders than a 290x.

Due to this in some games a R9 290x 4g is actually faster than a RX480 4g. I do not believe this is the case when its 290x 4g vs Rx480 8g. The quantity of memory can make up for the lower shader count.

The only true advantage it offers is as zanzabar stated power consumption. I would add to that with saying in general it OC's a lot better as well ( compared to a 290X )

Obviously it was not intended to be a top tier part either ala 290X 390 Fury etc.