not a United nor a Real Madrid fan, but if I'd to choose between either, Ronaldo any day. Simply put, he's the best athlete the game has ever seen, and arguably the best player right now, challenged only by Messi. Ronaldo would immediately provide an outrageous amount of goals for any team, and along with those goals, titles. Bale is considerable in the long-run, but he's in the same league as Reus, Hazard, Sanchez, Robben, Neymar, Pogba, Gotze etc who're all equivalently good.