As far as I understand it, Nero does encode the file, though I do not think it does convert it.......(maybe it does)......from my personal experience (I'm using Nero 7), I always convert the files to VOB Compliant and then burn them, so I don't have any problems with picture and sound synchronication, which I've hearde some people complaining about....
The Super Converter converts the files quite fast and with VOB Compliant Nero doesn't bother anymore to encode the file, it burns it right away....