It seems that, on balance, UA is best (for both earning and redeeming), especially if you normally fly Y (or lower Econ classes). You never have to worry about what class you fly to get 100% of the miles, and redeeming is still a good deal in my opinion (TK, for example, required 5K more miles to redeem a saver North American or Hawaiian award than UA). I always redeem for Saver Awards as a rule, and I've gotten my desired flight almost everytime I wanted to (about 2-3 NA Savers a year, an occasional Hawaiian saver, or South American saver -- I never redeem for Europe).