I agree you can use a 12 string for anything you want to play. For me personally, I grew up on rock and metal, so it’s been 6 strings for a majority of my playing. In that genre though, I always liked the sounds of the specific classic 12 string songs like Wish You Were Here or Over the Hills and Far Away, and of course love playing the intro to Wanted Dead or Alive, and Zebra’s Who’s Behind the Door. Those two for sure sound better with 12. Of course you can play those on 6, but I got a 12 string to sound more like how it should, and feel you just really need a 12 string in your arsenal to do them justice. Besides, when you down-strum a 12 string, as David Gilmour and others say, there’s nothing like it.
Technique certainly plays a part in how nice they sound, and you probably already know there are quite a few videos on you-tube titled best songs to play on a 12 string, or top 10 12 string songs etc. Like opinions those lists all differ but I will even refer to those from time to time to remind me of what to play or what new song to add to my repertoire if I feel I’m in a rut. Bottom line is once you pick up a nice Guild 12 string with a proper setup, and start playing it, you’ll play whatever comes to mind and it’ll sound glorious, because man they are hard to put down.