I've raised and eaten both grain fed and grass fed, some others have raised and some I have raised. The meat is just....different. The difference is pretty drastic at times, like the difference between the pale yolked grocery store egg and the flaming orange yolk of a free range hen.
My own meat has always been better (by better I mean more to what it is that I personally desire). I kill my meat younger.......chickens, goats, cattle, hogs.........I like 'em young. Most beef and the future goats are killed at around 10-11 months.
With both grass fed and grain fed, there is a huge difference in the quality (tenderness, texture, and flavor) of an 11 month old and an 18 month old.
I also cook the grass fed stuff a little different, it's cooked slower and gentler, and unless its a steak on the grill, its wet roasted in the end.