I guess it all depends on your travel patterns, craz. I don't use my miles for business travel and any vacations I take almost always involve a Saturday night stay. Therefore, CO's 20K award ticket is a real bargain to me. In your situation, obviously the Saturday night stay is a big factor and you would be better off with DL or another carrier.

Incidentally, I continue to believe that AA miles are the most valuable. In addition to perhaps the best award availability in the industry, you can do a stop-over and an open-jaw on the same award ticket at no extra mileage. On CO stop-over tickets are 35K miles; on UA you can't do a stopover; I believe DL allows a stop-over or open jaw, but not both; not sure about US or others.