A medium-rare grass fed bison burger stacked on top of a medium-rare grass fed beef filet.
Seriously though, the amino and fat profiles are going to be very similar.
You can find a breakdown on all the fatty acids, amino acids, vitamins, minerals, and carbohydrates here.
Are you talking about buying a side for the freezer? If not, and you are just talking about buying individual cuts at the grocery store, why would you have to buy just one?
If you are talking about freezer storage I would just go with the one you prefer to eat more. The difference in nutritional value is negligible so just pick the one you think tastes better.
I would strongly prefer grass-fed cow or bison, over either animal fed with grain.
You have to be careful and check-out the rancher's website or info... Don't assume that any animal is grass-fed unless it is specifically described.
Apparently one can't assume that all bison is grass-fed, so if that's the reason for the choice, you'll want to investigate further:
Assuming equal price and both grass-fed, as others have said, let your taste guide you. Everytime I've tried bison it's been in a burger, and it was over-cooked. Since it seems so lean, it was unpalatably dry. I think just cooking it properly (medium or medium-rare) would solve that, though.
Bison is a lot closer to what our Paleolithic ancestors might have been eating. They're probably even closer to what early Americans ate than modern cows. What Bison is fed is an orthogonal issue.
I eat Cow none-the-less because for some reason you can only buy a few cuts of Bison and it's very expensive if even available.
Bison (which I call buffalo because everyone in my family does)! My boyfriend's grandparents raise award-winning buffalo in South Dakota. His grandparents have been raising buffalo for many years, they even feed the buffalo occasional apples & swear that mean bulls taste bad. I take their word for it! They also firmly believe in keeping the buffalo calm & happy with lots of room as much as possible, including killing them on site for butchering.
I always tell people if they have had buffalo and not liked it, that they got bad buffalo. His grandparents even talk about some of the other buffalo breeders that do more crowding, heavy grain-feeding, and use bad genetic animals-so, you do have to be careful about where you buy it from. I would think chances are higher that chain-grocery stores that sell it probably don't use higher quality buffalo.
Obviously I am biased because of the family connection but we really love it. BTW, his grandparents will feed the buffalo a little bit (emphasis on small amount) of grain a couple of weeks before slaughter. They say it really helps with the flavor. Now, they will refrain from this as well if requested. Personally, I really respect his grandparents and I don't care if our 2,000lb buffalo ate a little bit of grains for two weeks out of his 3year life. I would care if I had a mostly grain feed animal though.
You should try both before deciding and compare for taste. For example try ground beef vs. ground bison and similar cuts of both. The hubby and I find 100% pastured bison a bit leaner then 100% pastured beef and we like the fattier beef.
I also find the equivalent pastured bison cuts to be much pricer then pastured beef - sometimes almost double the price.
It also depends on how severe your health issues are. Some people are trying to heal their gut and have a beef allergy and so can only eat bison until their gut heals.
Whatever you get - try to get a variety of cuts for different nutrition in 100% pastured grass-fed range meat!
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