Is it more costly to raise cattle for beef or raise fish in aquacultures?
Cost of production is somewhat difficult to pin down, since much of that information is private.  However, consumer costs are widely available: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2954450/
I have managed to find a comparison of beef, pork, dairy, poultry, and eggs to plants in terms of protein, and broadly beef is the most inefficient of those (See Figure 3): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5899434/
This suggests (but does not prove) beef is probably the more inefficient of the two.