A bit of clarification. I like pasture fed beef (steers only) that are "finished off for 2-3 months on corn and maybe beets, before being butchered. They must be dry-aged for 2-4 weeks at the proper temperature and humidity.
So, I guess I like grass fed/corn fed beef the best!
And as Kuan pointed out, Prime, with its outstanding marbling of fat, is preferred.