My LBS said that all Bell helmets (I was shopping for a Bell at the time - they were on sale), offer about the same level of protection. The price is in the looks, color, vents, comfort, etc. They said just go with what is most comfortable and fits your head best. I personally was looking for something with a lot of vents and a visor.

I had bad luck with Giro liners coming apart on me within a couple of weeks after purchase and switched to Bell. Might have just been a bad one, but didn't want to risk it.