If the guys on the ground are having a no good very bad day then having fewer aircraft that can loiter longer is likely going to be better because every time an aircraft shows up there's a ramp up period while the pilot figures out WTF is going on down there and that ramp up period comes with reduced effectiveness and increased risk to the guys on the ground.

Also, time to target is very important. An F15 with the wrong munitions that's seconds away at mach 2 is much more helpful than an A10 that can put the hurt on an entire tank company but is minutes away.