Hey

I dont think its worth it to join to FF programs, because then your miles will be "split" and it will take longer to get to an elite status.

If you are flying in Economy, I love AC because it is one of the few that give a minimum of 100% miles in International (not US) economy. The worst for economy is probably SIA cause it gives 0 miles for many fares.

For Business, I hate AC because it only gives you 25% bonus if u are in J. C gets absolutely zilch bonus.

Depending on the tickets you use to fly, you can determine which program is best for you. My favourites are United, Air Canada and Lufthansa.

Hope this helps