It depends on what is your time horizont, it depends on your values, it depends on your actual problem right now.
What I said, is that, in my humble opinion, from my perspective, is more valuable to work on a way to make meat sustainable and affordable for all than to work on cloning.
To the extent that it's not it might be improved by genetic engineering, and I doubt that producing the same meat in vitro will be a net improvement in sustainability for a long time. Now you've replaced a natural organism that needs some fodder and produces CO^2 with an entire factory, employees to manage it etc.
Why do you think that's more sustainable? One of those processes relies on non-technology that existed before there were even humans around, and the other needs high-tech that we don't even have yet.
We can solve this in two way, or we stop eating meat or we start growing meat in a more sustainable way.
The problem is not something to look in the future, but it is something really tangible, to have an idea of the order of magnitude I will post here a strip for xkcd[1]
The "efficiency" of a cow is really low, it is estimate[2] that half of the energy you put into a cow is necessary just to keep it alive.
[2] http://www.angusjournal.com/ArticlePDF/1095_OptimumCow.pdf
The point should not to have more cattle, but to produce food in a more sustainable way.
In my opinion they should aim to produce meat in vitro.