For international award travel I have compared AA and UA. Here AA really leads UA significantly.

Also it is important to look at mileage bonuses, where I have been satisfied with United. Including special bonus opportunities (like the double mile IAD promo, current Hilton promo), online booking bonuses, Mileage Plus Dining, surveys, current 2500 miles delay bonus etc., the bonus opportunities have been quite good (significantly better than with NW, the airline I was elite with prior to UA).