I opt for neither at the moment. I have used Roxio but found it to lack in some functionality. I have tried Nero too and I must say it offers a lot of functions, tools and accesories. However, I found it slow and buggy.
I am now using Cyberlink DVD suite. It offers most of the tools that come with nero and is fast and hasnt spoilt any of my dvds as yet. I think I shall stick with it a little bit more.