A lot of the guys on the street use the chatterbox and swear by them. They prefer the model with the 5 mile radius. Two words of caution. First, they say that the voice activated system can be a pain if you have a loud exaust. Second, might want to check the legalities if your talking about a racing situation. I could be wrong, but I thought I read a thread that stated AMA sanctioned races forbid radio communication with a driver. I'm no expert so you might want to check with someone that knows what they are talking about.
Also, I talked to a guy about the install and he said it was a piece of cake.
Hope that helps.
jw