I'm considering buying a RC-F. I drove one without a sunroof and it had plenty of headroom. Another one is out of state and has a sunroof. How does the headroom between the two compare?

 

Mine has a sunroof and I have plenty of headroom but I'm not a tall guy, I'm only 5,7. If you can find a local RC300 or R350 with sunroof, you can test it for yourself since they're pretty much the same inside, except for the seats.

 

You have more headroom about 2 inches in the carbon fiber roof and steel roof versions. There is also the less known advantages (of you care), the CF version roof being about 40 lbs lighter right off the top and having a lot more rigidity (no risk of rattles and less pendulum effect)