Personally I'm a much bigger fan of Out for Blood. That's because I use Bloodwing often. If I didn't then I'd likely use Riotous Remedy. The problem I have with Riotous Remedy is that you can only receive up to 15% (LVL 5) of your health back from a kill and it takes 7 seconds to receive it all. While this can add up quickly (stack), I would much rather have Out for Blood which can bring back a much bigger health return and I can call it back whenever I like.
In other words, in my experience RR bring back health steadily but slowly whenever you kill someone. Out for Blood on the other hand brings back health very quickly whenever you attack with bloodwing. (One - Two hits can bring full health)
Don't get me wrong, I'm sure Riotous Remedey has its advantages, especially when plowing through alot of enemies but I just cant get behind it especially when I don't put any skill points in the gunslinger tree to begin with.