DL also has a program. DL and Transmedia participants are similar, but not identical (I got directories from both by mail yesterday). Transmedia's standard option is to get 20% (cash) off, which to me generally beats miles--except that one must use a special card. The airline programs tend to be linked directly to a credit card, which means that instead of a conscious decision the points can be a nice surprise.

Myleguy is probably right; I have heard that many of these programs are run by the same company.