I personally prefer the taste of grain fed over grass fed. There's a ranch in Montana (don't remember the name right now) that does grain fed, but quality grain (not the hormones & bad stuff).

Or if you want to jump the shark (to mix metaphors), go for Kobe / Waygu beef. The super expensive beef is supposed to be raised to include sake and beer as part of their diet! Though I've heard most of the sake & beer is more myth than fact.

I just looked up the menu at Ruth's Chris Steakhouse -- it mentions "corn fed beef". They should know what's best!