I researched both heavily, which hopefully you'll do too before you buy, and I hope I don't come oever as too biased, but I chose the nuvo. one of the big things for me was the keypads, I just liked the look and feel of the nuvo keypads better (your results may vary) and also the fact that nuvo's keypads have more buttons... also one of the big deals for me was that the nuvo has higher watts per zone.. which however, that point is moot if you add a amplifier to each zone.
also I have a matrix switcher for video, so the cav's ability to switch video did nothing for me, however that may be something you want and or need.
one thing the cav / cam have on the nuvo right now is that its more heavily supported software wise (everyone's got a plugin for it) while the nuvo is still catching up (I believe so far only cqc and main lobby and casatunes support it for pc music playback -- I'm hoping someone writes a jrmc module for it soon) ...
also (semi biased as I can't speak for russound's tech support someone else can chime in with their experiences) I have to say kilowatt (yeah that's what he likes to be called) over at nuvo tech support has been the absolute easiest person I've ever had to deal with tech support wise, and that says a lot to me about the company.. not to mention their product..
in the end, as always test both systems at your local a/v store if possible, read both manuals of both products.. and I can't comment too much on the hi-fi system but definetly look into whether its compatible with other systems and programs like the cav and concerto are (you know in case you ever come over to the other side and get an elk m1), because there might not be drivers for it in case you want to make your own music server to push music through it later...
as always ask away if you have any more questions!