I will bring up this image again.
The heroes have much better pieces than the Bionicle small sets, and honestly, I think the helmets are better too.
Sure, Bionicle had some great sets and pieces, but most of the canister sets re-used the same Inika build. Hero Factory has a little bit of originality, as the villains (except for Von Nebula and Rotor) don't use an Inika Torso. If you don't like the HF sets, just modify or revamp them.
Hero Factory also doesn't have much of a story, making it easier for kids to play with the sets. Bionicle, on the other hand, has a very complicated story, and I recently found out (on a MMOG) that most people didn't like Bionicle because of it's complicated storyline.