Great topic and I have posted on a flyer website on this subject as well.
It is not always about what card will provide the greatest rewards, but in which PROGRAM you can maximize your earnings. I strongly suggest to many i speak with, Champion ONE program that will be the best fit with your spending and travel, including partners and bonuses... and consolidate everything you do to that program.
I have personally chosen Aeroplan. I can consolidate all of my earnings to the Aeroplan program from Credit Card expenses to air travel, to hotels, to car rentals, and they offer 1.5 Miles/$ for purchases on Gas, Grocery, and Pharmacy. So fill up at Esso and you are earning 5.5 miles per $3 spent (1.5/$1 plus Esso partner at 1/$3)
It makes absolutley no sense to collect miles or points into different programs. You will end up with a few here and a few there, never enough to do anything with!
I do however suggest a back-up Points/Milage account. The one that made sense to us was the Alsaska Milage PLan program. MP covers every other airline (from both One World and Sky Team) that the Air canada (Star Alliance) does not cover. This has proven success with personal and business travel. Other then unaffiliated LCC, you never really have to worky what airline you fly, just go for the most economical affiliate.
So study your spending, the Air Alliance you can most commonly fly, focus on program partners, and keep an eye out for bonuses. We earn around 80,000-100,000 Aeroplan miles per year on about $36,000 in spending on a Credit card by utilizing partners and air travel.
Also, when booking air reward travel with a FF program, if the price is right, do not be affraid to pay for the seat of the primary account holder. You will then earn reward miles INSTEAD of using them. I always cover the cost of my family utilizing rewards and pay for my own.
An example is as follows:
4 of flying to YYZ-MCO. Total Aeroplan miles = 100,000
Aerplan Miles remaining in after trip account = 0
VS
4 YYZ or BUF-MCO, with 3 on reward seats and 1 Paid = 75,000
Aeroplan miles remaining in account = 25,000
Aerplan Miles earned on trip to MCO= Est. 2,000
Total Aerplan Miles in Account after trip = Est. 27,000
Total cost of having additional 27,000 miles = Est. $170-400
Now, you already have enough for 1+ sests of your next trip and you only need to earn 48K more miles.
I hope this helps and makes sense.