FIFT.
Put it this way: the F-15I is a known, combat proved warbird and well worth upgrading. The F-35 is growing more expensive by the day (that means fewer airframes can be bought) and is totally unproven in combat. If you want to use the F-35 in the strike role, then you’ve got to mount the majority of weapons externally. That totally negates any stealthy features. Besides, the F-15I carries more ordnance and is a better bomb truck.