I have watched the Chima episodes, and two of the Hero Factory episodes, namely Ordeal of Fire and Brain Attack. And the Hero Factory shows beat Chima hands down. Here are my reasons:
1: The animation quality of the HF shows is far superior to that of Chima.
2: The HF shows have a more interesting premise than Chima.
3: Hero Factory is just an all around more interesting franchise than Chima, in my opinion.
The HF shows can be silly, but in an entertaining way, and can actually be an enjoyable show sometimes. Ill be frank, the Chima shows are just dumb to me.
Maybe someday I'll get around to watching the Ninjago series. I'm seeing quite a bit of positive feedback.