I use both, but the '!bang' syntax is more convenient when you simply want to repeat a search using a different search engine, or want to use an engine you don'

I use both, but the '!bang' syntax is more convenient when you simply want to repeat a search using a different search engine, or want to use an engine you don't have a quicksearch for (you could of course add them, but sometimes it's just not worth the trouble for the few times you need it).