I have a Blackwidow and I think it's a great keyboard, but then I realized that I never need macro keys (used to actually not like it cause I pressed M5 instead of ctrl), that I really didn't need backlighting, and that the f-row keys are shifted too much to the right for my taste (For SC and stuff...)... Also I thought the keyboard was too big. Which is why I ordered a Choc-mini, which seemed to fix these issues and also have the f-keys closer.
But these are all personal issues, so I would say that an actual negative of the keyboard would be its finish... it's glossy plastic which looks AMAZING when you first take it out of the box... but once you take off the plastic cover, you will never win the battle of grime and fingerprints that show up on the thing.
Ultimately I would say go by preference... maybe take notes on your posture and how you use your keyboard over the course of the day? I like my Blackwidow very much and I haven't really had the problems with keys or bad switches like some other people had, but if you look at the 2 keyboards you are getting, it is definitely much easier to return the Blackwidow at Fry's if it is defective for exchange than the Choc Mini.