You spend most of your time under a hood or with foggles, leaving the (non-navigational) situational awareness and the vigilance for other traffic to your trusted friend in the RHS with tig hours.
A priori, you could say there is a safety argument for doing your training in controlled airspace, as the RHS then generally doesn't constantly have to divide attention between looking outside and instructing you. But I dare say most instructors can cope with that.
I was actually went on a bit of a tangent and was just talking about flying in general, not IR specific.