I have a Giro Atmos and a Bell Furio. The Atmos vents really help, I was a skeptic when my husband claimed that but the ventilation really does help.
I prefer Bell to Giro because you can adjust the tension on the bike with their GPS system but I liked the Pink Atmos. 
Bell makes Giro but Giro uses the Roc-Loc adjustment system.
Amanda
2011 Specialized Epic Comp 29er | Specialized Phenom | "Marie Laveau"
2007 Cannondale Synapse Carbon Road | Selle Italia Lady Gel Flow | "Miranda"
You don't have to be great to get started, but you do have to get started to be great. -Lee J. Colan