I got a Mophie case. It's pretty sweet, and not very bulky at all.
These look really nice and it was one that i considered before getting my ravpower one. Mophie was just too pricey for me =(
IMHO, it's up to your use and preference. I stuck with Mophie because their white case wasn't matte, so it wouldn't get dirty easily. Plus, they do have a nice capacity for their powerstations, and I did get a corporate discount for them. But if you're interested in another brand, I would recommend the XtremeMac as well. I do like the kickstand feature for one of their cases