I like both Parmesan and Romano on pasta, but honestly, I prefer Romano in most uses where people may typically go for Parmesan. I like the creamier, tangier flavor of it, as opposed to the more bitter, nuttier flavor of Parmesan. Parmesan can sometimes be too strong for my tastes in certain dishes. Plus Romano is a bit more versatile in that if you top something with it, then bake/broil it and let it toast up a bit, it will take on those nuttier notes of Parmesan if you are in the mood for that.
I also really enjoy using Romano as part of an overall blend of cheeses when making a cheese sauce to go with pasta or over vegetables.