it very much depends on your flight-patterns, and for which flight-classes you (or your company...) pays.

mileage-credits: base-credits vary already from 50% (Thai-eco) to 300% (Lufthansa first).

status-mileage-credits vary from 50% (Tahi-eco) to also 300% on Lufthansa.

Mileage-Limit for highest status-category vary in some programs depending on your resident-country (Lufthansa).

the preferred program may change for members depending on future day-to-day-decisions of the airlines (my case: UA gave up direct flights IAD-Switzerland on march-1st-98, but I am only about 300'000 miles away from achieving life-long-PremEx-membership when I pass 1Mio miles flown; if you read one of baobab's latest "rumours" UA may be thinking of flying Tel-Aviv-USA in 99).