Yeah, it would be real cool to control the earth but Raven can do so much more. I mean, I'd choose flying, healing, mind-reading, tele-transportation and all the other cool stuff other making rocks move any day.
Oh yeah. And with all those books full of different spells and stuff. And in the Teen Titans Go! comic, it is also revealed that she can travel in a kind of soul form, like a raven figure for about five minutes (not too long but apparently it's exhausting). Magic is the best.