I was an engine technician on F-15's A's through D's, with a three year stint on F-4G Wild Weasels. As a QA inspector, I was involved with the operational testing of the GE-110 on the F-15E. Besides performance capabilities, logistics need to be considered. The GE-110 engines we tested did not have a simple side-to-side interchangeability like the P&W's did. The F100-PW-200/220 series engines were easily interchangeable between airframes (F-15 to F-16 and vise-versa), and LH to RH on the Eagle, where the GE engine required significant engine to airframe connection modifications. Also, parts supply and procurement has to be considered. Some units operate multiple airframes, Air Expeditionary for example. It reduces your logistics tail to have subsystem interchangeability amongst different weapons platforms as much as possible. Having F-16's with a different engine from your F-15's, for example, increases the size of spare parts warehousing and tracking across the entire fleet, increasing the likelihood of procurement mistakes (getting the wrong part) and shortfalls (not having adequate numbers). I will venture, that many of the foreign procurement sales, getting the GE over the P&W, have more to do with "secret handshakes," State Department and foreign government lobbying (the CEO of GE was one of Obama's "Czars"), and some sort of special interest kickbacks, over outright performance. As it is, the P&W F100 series engines are becoming legacy. The F119-PW-100 is their new shiny toy. Maintaining support for foreign sales is sometimes not as lucrative.