I would disagree on that. The best miles earned are always going to be where you have the most chance to use them. If OP flies SQ once, and never again, what good are those few thousand miles credited? They have a choice of *any* star alliance carrier to credit to.

vnfilm1 , the answer depends on whether you plan to fly more Star Alliance flights, whether you already have some UA miles collected, whether you have any other Star Alliance program affiliation as well? Will you plan to attain status on any of the airlines? Where do you plan to redeem your award tickets (e.g. you can get one-ways in Europe for as little as 6000 UA miles)? Unfortunately, the only "simple" answer you can get to your question is: "it depends."