...is to be avoided. Essentially, there are two three problems. First, although farming may seem as if it's more sustainable, it's actually terrible for the environment. Second, as Schrambling correctly notes, it's very bland. And last, tilapia generally lacks the nutritional benefits of other seafood. Even farmed salmon is much higher in Omega-3 fatty acids:
[New York Times, May 2 2011]
There are better alternatives available -- trout, for example, is much healthier and tastier and generally not a lot more expensive than tilapia.