Difficult. I think Heavy Cav in RTR carries quite a punch due to a high charge bonus. Hitting from behind, they will most likely rout any infantry with the second charge. But: in RTR Heavy Cav is ****ing expensive.
I think in EB Heavy Cav isn't so powerful. You'll need some more charges there.

But why are you trying to decide anyway? They are both beautiful mods, where thousands of hours went into. You should play them both otherwise you'll really miss something.