Air Canada offers 10,000 bonus points for every 10,000 points earned starting at 50,000 (i.e when you reach 50,000 qualifying miles, you get an additional 10,000, when you reach 60,000 qualifying you get another 10,000 etc.) This is like a 100% bonus on United for the same mileage level. There is no corresponding 25% bonus on Air Canada starting at lower levels. To weigh which program you want is difficult but should be based on which country you fly most frequently in. Maple Leaf and associated lounge access (see Air Canada's site for which lounges are always open to you when travelling on Air Canada)is free for Elite and super elite while you have to pay 200-300 U.S. to get Red Carpet (unless you are always flying Business or First Class). Some special bonuses are only available to US members on United etc. etc. Each person has to look at their circumstances to determine which will work better for them. For me, Aeroplan has been right as I travel mostly in Canada with occasional US and European trips.