Having done both, if it's a choice between Europe in Nov/Dec and South America, I would definitely go for South America - much, much more bang for your buck.
I'm sure you'll still enjoy your trip, but Europe is really not at it's best in Nov/Dec and just about all the camp grounds will be shut. It's also bloody expensive (I live here). If you do come, it's worth joining a Youth Hostels Association - the hostels are pretty good in Northern/Western Europe.