Just an upscale. From what I know, everything else seems to be the same. That is, story, equipment, so on and so forth. Even DLCs are the same.
I'm actually Ram > Rom, but I like them both. I see that our tastes never seem to align in this series.
I've always noticed that Rom would be stronger than Ram in my party. It might have something to do with the elemental property of their attacks though. I give Ram the non-elemental magic, while Rom gets the elemental ones. Probably something to do with that.