Hawking radiation propulsion has the perfect specific impulse: exhaust velocity is the speed of light. Black hole hawking radiation also is perfectly efficient: 100% of the mass is converted into energy. D-T fusion only converts 0.4% of the mass to energy.

There are many awful engineering problems of a black hole drive, but they're not so bad as to dismiss out of hand. See https://arxiv.org/abs/0908.1803v1