Is it better to try to get into TSA Pre-Check by applying through an airline or though Global Entry?

Obtaining membership to TSA Pre-Check through Global Entry instead of through an airline frequent flyer program has some advantages. When done through an airline the member is only eligible to be considered for Pre-Check benefits when flying on that airline whereas membership through Global Entry allows the traveler to be consider on any of the TSA Pre-Check member airlines (American, Alaska, Delta, United, USAirways, and soon Virgin America). Also, there is anecdotal evidence that TSA Pre-check members who are also Global Entry members are selected for the expedited service a greater percentage of the time than folks who are not members of Global Entry.