IMO, SD is better for the more extreme setups. If offers better control over the a/f ratio.
The only negative thing I've noticed with SD is the throttle response isn't as snappy. It's a bit slow, not slow enough the average person will know, but if you've had a nice snappy, perfect maf tune, then go to the sd tune, you can tell.
But when comparing it to maf for performance, imo, there's no comparison. It takes longer and yes, it changes just a bit with conditions, but not enough to worry about. I may see .2 difference in a/f ratio from one extreme to the other.
In my situation, I tuned SD because boost with a turbo isn't as predictable with the other chargers. I can get 5psi going up a hill in fourth, then I can get 5psi in 1st at 4,000rpms (depending how warm the turbo is), so you can see how difficult it is to tune for boost when there are no tables to adjust (like maf tuning).
Now, the tune richens up right where I need it when boost comes on, regardless of rpm.
If you have a head cam setup, I always try to tune with the maf first, if that doesn't work, (which it hasn't yet), then we'll go sd.

later,
allen