Roxio is supposedly easier to use....
I prefer nero as it's more customizable, and gives you better blow-by-blow info on the burn process. (roxio is a simple progress meter)
Nero comes bundled with "NERO EXPRESS" which is a "dumbed down" interface for the novice, but also has the full fledged nero that's got enough settings and tweaks available to make even the most advanced user happy for a long long time