It depends. If you're riding on the road with a group, then probably the road bike is best. If you're alone and want to have a smoother ride, then a cross bike with road 32's at 50-60 psi would maybe make more sense. I'd definitely say the cross bike if you're riding on a rails-to-trails path or something that isn't completely paved.
It doesn't really matter. The important part is you get the miles in. I would say that riding your cross bike at least once a week is a good thing because it will probably have a somewhat different fit and you should be comfortable with it.