496fe,
Both height and width count.
When we sit in my car the rollbars are above our helmets by about 2" to 3". Width is important mainly if you have a passenger, which was the case when we flipped on the track, or if you have a wife who asks "where's mine....?"
In either case I can attest to the efficacy of being able to answer that query affirmatively!
Finally, you are the arbiter - it's your car, and therefore your decision. Having said that, I know what I'd do
Enjoy,
Tom