I have one star alliance (united) and one sky team (air france) mileage plan but im willing to switch my united for another star alliance plan.

see the thing is, the united mileage expires fast, and i feel like i dont get enough miles (consideirng how much i fly) especially compared to the air france plan i have. im not complaining. im just wanting to change.

im considered one of the following:
- air canada's aeroplan
- singapore airlines krisflyer
- ana mileage club

1. does anyone know where i can find a site that compares the 3 frequent flyer programs?
2. which one has the longest mileage expiry year?
3. which one would you recommend?

thank yu