Actually, if the programs are teaching basically the same stuff with only a change in sequencing, what you are describing is more likely massed vs. distributed practice because rather than breadth vs. depth. It sounds like SfA is using a stranded design and ASP could be using a spiraling design. The stranded design is specifically designed to distribute practice while the spiraled design typically repeats or reviews material after long intervals.

The is a "mountain of evidence" that shows that distributed practice works better than massed practice and that stranded curricula work better than spiraling curricula. I'd suggest reading Daniel Willingham's article Allocating Student Study Time: Massed" versus "Distributed" Practice for a good overview.

Not surprisingly, the two most successful interventions, DI and SfA, use stranded designs. In contrast, most commercially available curricula use the more fashionable spiraling design. Also, not surprisingly, your typical commercially available curricula doesn't work very well and there exists the resultant calls for reform.

Here is Engelmann (of DI fame) on why the spiraling curricula fails:

Typically about 60 school days pass before any topic is revisited [in the spiral curriculum]. Stated differently, the spiral curriculum is exposure, not teaching. You don't "teach" something and put it back on the shelf for 60 days. It doesn't have a shelf-life of more than a few days. It would be outrageous enough to do that with one topic-- let alone all of them.

...Don't they know that if something is just taught, it will atrophy the fast way if it is not reinforced, kindled, and used? Don't they know that the suggested "revisiting of topics" requires putting stuff that has been recently taught on the shelf where it will shrivel up? Don't they know that the constant "reteaching" and "relearning" of topics that have gone stale from three months of disuse is so inefficient and impractical that it will lead not to "teaching" but to mere exposure? And don't they know that when the "teaching" becomes mere exposure, kids will understandably figure out that they are not expected to learn and that they'll develop adaptive attitudes like, "We're doing this ugly geometry again, but don't worry. It'll soon go away and we won't see it for a long time"?