That's a bit of a pick-em - totally comes down to personal brand preference. If you're not willing to OC at all yourself, the MSI card comes with higher factory clocks and will perform better out of the box.
However, you're more likely to be limited in your overclocking by luck of the draw than by which design you pick. I'd probably get the MSI card just because I've heard a lot of good things about their TF designs, but certainly people say a lot of good things about ASUS too.
You're not gonna go wrong either way