In my experience, LRF has a bigger font size, so that would mean more page turns. I also find that the LRF font seems to be darker than the epub (maybe also because font size seems bigger?).
Epub also only has left justification, so if that's an issue for you, you should go LRF. I've been reading that epub is going to be the standard for ebook formats though.
I'm still on the fence myself as to which format I prefer