DON'T RUSH INTO BUYING EITHER.
...until you get the chance to handle/hold them both.
I've owned 3 Ak rifles over time...and now have another. Honestly...I like the look of them, but I just don't like the handling/fit (although this last one might be a keeper). For whatever reason I've always gravitated back to M4 style rifles.
Get out to some games...try to get a rental (although it's doubtful that someone's going to rent you a RS 56) from one of the other players. You may find that you have a real handling preference for one over the other.
...you'll eventually end up with both...but that's later...
Have fund, best of luck,