Not only do markets appreciate beef, but they will pay top dollar for fancy high-quality beef. Once someone gets growing beef down, it probably won't be much of a stretch to develop top-quality sirloin, and more repeatably.

Additionally, beef is a good target ecologically speaking. Fish and birds are much more efficient at energy conversion, so there's a much larger margin of energy and material savings to be had with beef. As yet even another bonus, I suspect the ratio of edible meat to body mass in beef is much lower than in fish.