The only time I've liked "hard" music - was when I went through a rebellious stage as a teen & when I'm in a bad mood (which incidentally is at the moment)... It helps to empathize with my feelings but then I soon prefer something more happy, like you mentioned.
Just the other day, I heard about an experiment with water crystals & plants... after being exposed to heavy metal music, the plants didn't do as well & the crystals were significantly different... compared to "happier" music & positivity. Sorry, I don't know the source, but you could google it.
Beethoven actually has some good music, IMO, to empathize with anger & then bring me back to a more peaceful place/feeling... esp. 9th...
http://www.youtube.com/watch?v=YAOTCtW9v0M