In terms of health it will change the omega-6 to omega-3 ratio. Grass-fed animals typically have more omega-3s. The flavor also changes. Better or worse depends on the person eating its preference. We believe corn fed have a more bland taste and smell. Others describe grass fed as more gamey. Grass finished can vary a lot. We have been finishing on alfalfa and think it improves flavor over finishing on fescue. It will likely gain fat with corn fed. That does not necessarily mean better. Your ground beef will be a lot soupier. All that said it will be a big upgrade from fast food beef and supermarket beef!