Pick what you know the best. You will waste time in learning something new instead of working on your product. When time comes, you can always optimize it(writ

Pick what you know the best. You will waste time in learning something new instead of working on your product. When time comes, you can always optimize it(writing performance critical parts in c), or pay guys who are better than you to "translate" your app to another language. God knows i'm not following this advice, but please do not fall into a "premature optimization" trap.