When I am confronted with a situation that puts two people at comparison and I am expected to chose the better based on my preferences, rather than use what is lacking in one to compliment the other, I express my preference without stating qualities.
Q: Who is more beautiful?
Me: I prefer her features to hers.
Q: Which food tastes better?
Me: My taste buds agrees with that taste than the other.
Q: Who is smarter?
Me: I prefer his representation of intelligence to hers.
Doing this makes me sleep better at night and at times earns me more friends.