I am a big fan of the Harvard school of public health. I was reading this article on their website about the Paleo diet and came across this information about grass-fed beef.￼ Although some grass fed beef may have more omega-3 fatty acids than commercial beef, the amount that is produced in even the highest samples is still about 10 times lower than an equivalent amount of fatty fish.￼ ￼ in other words, there is a growing body of evidence that there is little or no upside to eating beef. At least not evidence that meets what Valter Longo calls the five pillars of longevity.￼
Grass-fed beef is often highlighted on the diet, which is promoted to contain more omega-3 fats than conventional beef (due to being fed grass instead of grain). It does contain small amounts of alpha-linolenic acid (ALA), a precursor to EPA and DHA. However, only a small proportion of ALA can be converted in the body to long-chain omega-3 fatty acids (EPA and DHA). The amount of omega-3 is also highly variable depending on the exact feeding regimen and differences in fat metabolism among cattle breeds.  In general, the amount of omega-3 in grass-fed beef is much lower than that in oily marine fish.  Cooked salmon contains 1000-2000 mg of EPA/DHA per 3-ounce portion, whereas 3 ounces of grass-fed beef contains about 20-200 mg of ALA.
The other thing you often hear from many optimum nutrition advocates, especially those are influenced by Paleo diet pseudoscience is this concept of getting the ratios of omega-3 and omega-6 polyunsaturated fatty acids in the right ratios. Again, according to the Harvard school of public health:
￼One question that some people have had is whether the polyunsaturated fats, specifically omega-6 polyunsaturated fats, are pro-inflammatory. There’s a myth going around that omega-6 polyunsaturated fats are toxic and pro-inflammatory and bad for us. That’s based on zero data, really. And this study showed that omega-6 polyunsaturated fats were the best of all. In fact, they were what was driving the majority of the benefit of overall polyunsaturated fat and also total fat.