Actually, our own Galaxy's Supermassive Blackhole is larger.
This is comparing NGC 1365's Supermassive Black Hole (Over 2 Million Miles wide) vs Sagittarius A* (28 Million Miles wide)
Sagittarius A* is lager than Polaris; The largest Star that makes up the Big Dipper.
Here is comparing Polaris to our own Sun.
Our sun is the small orange sphere on the far left. Polaris is the second larger blue star in from the right. (Rigal is the star behind Polaris)
The Sagittarius A* is between the sizes of Polaris and Rigal. (Closer to the size of Polaris by a few million miles)
If Milky Way's outer arms is moving 155 miles a sec in one direction (This is how fast our Solar System is traveling around the Milky Way), then that would mean the the Center of the Milky Way (Where the Supermassive Black hole is) is spinning much much faster. Near light speed.
I remember that black holes don't spin. Neutron Stars spin. Black Hole's pulls light in via its gravity, but since light moves in an omni direction, the gravity of the black hole sucks in that light, pulling it in one direction. So that would mean that the light is the one that is spinning or spiraling down into the black hole.... Therefore, the spinning is as fast as light (or faster), not "near the speed of light".