Hi Scott,
Excellent question my friend!
Sadly, there are no right or wrong answers here. If it were me, I would go with the R&S first because today's UC implementations are so network dependent and so intertwined. I've always felt that my low level understanding of networking has held me back and if I had to do it all over again I would build a solid understanding of R&S as a first step. Of course, only you know what your current and future career goals are, so this advice may not completely jive with your knowledge levels and current job responsibilities.
You can't really go wrong either way....cause as they say "knowledge is power!"
Cheers!
Rob