Early/Mid Game you generally have to make a quick choice to go Roaches vs Banelings.
In my experience both units are very powerful for tier 1, but I've had a little more success with Banelings vs Terran (unless they go mauraders) and Roaches vs Zerg.
Mass Banelings have ended a lot of games early for me, but I'm not sure if they're worth going until I have a sizable roach force.
Which do you tend to go first?