Whose frequent flier program is best?

that depends on a lot of different factors, including:

1) Do you fly international, or only domestic?
2) Do you fly cross country, or short-haul flights only?
3) Do you frequently have to cancel and/or change your flights after booking?
4) How important are upgrades to first-class, priority boarding, etc?
5) Do you rent cars and/or book hotels when you travel, to contribute toward your FF account?

You might want to head over to a site like http://www.flyertalk.com for in-depth discussions of different programs.

Alaska Airlines. they still remember what a flying customer is all about in their service. you can combine many airlines airmiles with other airlines or partners.

Mostly San Francisco to the East coast or Europe. Don’t generally have to change tickets after booking. I’d like things like upgrades etc if possible, but it’s not necessary.

From San Francisco stick with United. Most of there trans con flights are great and you can do red eyes if you want. Usually several seats open so you can get an empty next to you if you like. Also they have a great FF program that will let you upgrade pretty quickly.

In Europe, Britishairways