Two reasons for the road tape on my bars rather than grips.
The first reason is that I like skinny grips so I have good reach to the brake levers (one finger braking, thanks Shimano) so road tape tends to be quite skinny but still cushions my hands. This is good for us girls with smaller hands.
The second reason is the cork road tape tends to be less slippery than rubber grips... or at least that is what I think.
At the end of the day, it is a habit I have gotten into since my mtb days that I have no intention of breaking. Now that I am with Profile I have tons of choices in bar tape colors so now my tape can be a fashion statement.
