Also depends what you want it for, a toy for track days and fun on the road the ra is better but for everyday driving, commuting etc. the wrx has the edge.
The ra has shorter gearing so it always revving it's n@ts off on the motorway, this combined with less sound deadening make it a lot less user friendly. Also the ra has dccd (if its the sti) which makes driving fun.
But for me it would have to be the ra, easy.
Johnny