From what I have been reading most airlines have an exception for military fighter jet time. I believe F-16 and F-15 time would be looked at equally since they both are fighters but I'm not an airline guy so I can't answer for sure. The emphasis of having twin time is for the experience of flying engine out with asymetric power. This can be challenging in aircraft with engines mounted on the wing. I would imagine the F-15 performs very similar to an inline fighter (F-16) with one engine out. The fighter guys around here may be able to give a better answer.