I'm a big fan of equipment grounding conductors other than the raceway or cable armor. You have already pointed out the major drawback, the connector may be loose & you lose the equipment ground.
As for other advantages, all you have to do is compare "uses permitted" 333-3 & 334-3.
The only additional advantages I can think of are that MC doesn't require the use of bushings, & AC, to the best of my knowledge, is not available with an aluminum jacket. A roll of steel jacketed AC is really heavy.
Tom
[This message has been edited by Tom (edited 06-08-2001).]
