I tried BBSmart and Empower. The results are similar and BBSmart is more full featured. If I was going just for price, I would have gone Empower but a couple of things bother me about Empower.

Empower by default overlays your signature with their advertisement. Yes its true there is an option to turn it off but it shouldn't be there in the first place. When I did the trial, I was shocked as I didn't realize they did this and found the setting myself. Why even have that in your software?