There is still a big difference from grass fed beef and bison and the leaner meats like elk and venison have a much different flavor and they seem more difficult for me to cook right. I love venison, for example, but I don't always nail it. And it usually helps to spice it or sauce it.
If you are used to that and then try a steak from a strictly pasture (grass) fed cow, it will have a distinctly different flavor.