No BIG advantages that I know of. If all you're doing is playing back video and you don't want to know where it came from, how it was compressed, etc. because of it's non-commercial nature, VLC is able to include a lot of code that would cost any commercial enterprise a LOT of money to license...definitely not the kind of software any for-profit company would be able to offer for free and stay in business for any length of time.
The only advantage QuickTime has in that it plays QuickTime content better than VLC... ie movies with multiple sprite tracks, chapter tracks, media skins, etc.
If most of what you want to play is NOT going to be QuickTime, then VLC is probably your best (and free) bet.