The F-15SE is a variant of the F-15 Strike Eagle (F-15E), which is itself a variant of the original F-15 Eagle.
The F-15SE has a top speed of Mach 2.5 (1855 MPH), versus Mach 1.5 to 1.8 (1113 to 1335 MPH) for the F-35A (the Air Force variant). The F-15SE also has a longer mission radius of between 1333 kilometers to 1667 km for an air-to-air loadout, and a mission radius of between 1482 km to 1852 km for a air-to-ground loadout. In comparison, the F-35A has a mission radius of 1082km which is 11km under the Air Force's requirements.
However, the F-15SE's main advantage lies in it's cost, 1 F-15 would cost about 100 million dollars, versus the F-35A which costs 193 million dollars in the LRIP-5 (Low Rate Initial Production) batch in fiscal year 2012. On top of this the F-15SE is actually a stealth aircraft, Boeing has converted the F-15E's CFTs (Conformal Fuel Tanks) into CWBs (Conformal Weapons Bay), which can carry either air-to-air weapons (AIM-120, AIM-9X) or air-to-ground weapons (SDB, JDAM).
With the Air Force approaching a fighter shortfall, and the two replacements for early model F-15s and F-16s (F-22 and the F-35) not meeting expectations, there is serious need for a fighter to close the gap.
Photo Credit: Aviation Earth