If you want the BEST, then you only get one of them.
If there were two different BESTs, then we would have to decide
whether one best is bester than the other best or whether they're
both equally best.
Red giants, white dwarfs, and main sequence stars are not
particularly strong emitters of X-rays, but they do emit lots of
other stuff that makes them easy to find.
Black holes don't emit anything, so no matter what kind of detector
you're using, they're tough to find.
Neutron stars are strong emitters of X-rays and not much else.
So an X-ray detector is just the thing to use to find them.
