Deco is definately the more effective option right now, but that doesn't mean that I'd rather have him on my team if i were building a roster. To start off, i hate his diving and all the antics he has - but he has proven to be deadly on counter attacks and at times he has his moments of brilliance. For the most part, though, i find him to be an average player and very overrated by the media and fans who think he is even world class material.
Ronaldo, on the other hand, has all the potential in the world. He's still trying to figure out what type of ways to play, which has lead to him being very inconsistent. Given some time, I expect him to solidify his place as not only one of the world's greatest talents, but one of the best. A very gifted winger, once he manages to tone down his shows and does what is best for the team, the sky's the limit for Cristiano.