If you make a black hole at one of your empire's chokepoints, you can then decide whether to fight with shields or without.
Just move from one side of the wormhole to the other, and you get to disable the enemy shields OR make full advantage of your own.
You can put shields on your ships and fight outside the BH, or use armor & long-range WMGs to fight inside the blackhole.
The enemy has a 50/50 chance of guessing correctly, and will either have useless shields(by BH) or few shield points(by design), if they guess wrong. In case they guess right, you can use the other strategies mentioned in this thread.
Armored boarding ships in a Blackhole system would rule against baseships, since his shields would be gone
