These two creatures require vastly different habitats. If it were easy to maintain a pond, with no water shortage, I would expect fish to produce more value per acre.
Catch-and-release is a much simpler proposition with fish than it would be with cattle, should you choose to invite Sportsmen to join you.
I think the start-up and maintenance costs might be less for fish than for cows. My neighbor across the road feeds his cows year-round on purchased hay, and needs a large tractor to move the bales. He has quite an infrastructure of pens and feedlots also. I should think the handling equipment for fish would be less than for cows.
Most fish farms spend quite a bit on aeration, filtration, and pumping water.
Why not do both?
"You must be the change you want to see in the world." "First they ignore you, then they laugh at you, then they fight you, then you win." --Mahatma Gandhi
"Preach the Gospel always, and if necessary, use words." --Francis of Assisi.
"Family farms work when the whole family works the farm." -- Adam Klaus
I'm not talking about a fish farm, I'm talking about a pond, or multiple ponds. And of course there's no reason you couldn't have both fish and cows if you had the money to invest in two enterprises.