I called the shop, the person understood English, but didn't really speak much. They told me that on Sunday someone who speaks English would be there. I'll post when I have price info.
About the preference, to each his own, like Vorsteiner, get the VRS.
The VRS Diffuser doesn't do much aerodynamically, it's more of an aesthetic add-on, I don't think it's dry CF anyway (someone can correct me if it is). I'm not a big fan of everything CF, so I'd get this one to try out. Their blog says they were planning a CF one (that was back in May).