Re:Here are the main differences (Score 1)

There is a way to allocate "typed" memory through Boehm. If you always use the "right" allocation routines, no memory will be scanned which doesn't need to be.

That statement is false. The Boehm collector always scans the stack conservatively; it is neither type-accurate nor liveness-accurate. So memory which is pointed to from the stack can be scanned unnecessarily.