I thought both were fantastic. I probably liked Bad Sisters more but both were really well done. For me they both felt like series that were really self contained in the one season and shouldn't continue, but I heard they might be making another season of Bad Sisters.
I finished watching Black Bird last night. It was only six total episodes and was Ray Liotta's final performance. It felt a little bit like it wrapped up too quickly toward the end, but maybe that was because of Liotta's death. Overall, the series was pretty good. I recommend it to anyone if you have the time. It's based on actual events.