Auto Focus

[iND]

Now that I have my 5D Mark III, I feel like I need to relearn autofocus to take advantage of the plethora of options.

I want to discuss the AF modes

SINGLE SHOT
AL SERVO
AL FOCUS

ok single shot has been my standard for years, I use primarily single point for focus,
and frequently use of the AE (exposure) lock feature.
The Mark III now allows us to AE lock for multiple shots. This by itself is a great upgrade for me.

AL SERVO I use when I know the subject will be moving, but the MARK III allows a setting that the shots after the first in a sequence will not fire until the AF sets accurately, this by itself will increase keepers. This feature is greatly enhanced by additional suboptions.

AL FOCUS is where I have a void in knowledge, it is suggested that it acts like single shot but will switch to AL SERVO if the subject moves unexpectedly.

So what is the downside of AL FOCUS, and i question why have I never used it.
Sounds like the it could be the best of both worlds but there must be a downside somewhere.
I suspect AL FOCUS is slow.
I also wonder about AL SERVO if the camera is moving and not the subject?

Comments appreciated.
In the mean time I plan to stay with single shot AF and add the AE lock for multiple shots of the same subject.
Focus is just so critical to what I do (weddings) I don't want the camera system to make too many choices.
Now if I was shooting sports or wildlife then AL SERVO may be used with the larger autofocus areas.
I think I will leave AF FOCUS out unless someone can give me some real advantages.

Thank you