landon_3 :
I built my current computer a few months ago. Its actually a dell mobo in a Lenovo case. I bought the RX 460 so I could do some gaming with decent settings. I've had the 7850 for 3 years now and used it quite a bit until I got the 460. The 7850 layed around until I actually figured out that the 7850 was better performance than 460. So I went to put the card in my current build and now its not working in this pc. The pc it was originally ran in was a core 2 duo. My current build is a i3 2120
So looks like the system was working, and had the RX 460 in it, then you went to swap it fro the 7850 and now have no display after Windows loads.
Boot up with the RX 460, delete the AMD drivers, shut down, install the 7850, then install the drivers again.
As far as speed, the cards are very equal, but you can test them yourself once they are both working in the system.