There is a heavy overlap between the two, but my impression is that being scrappy has a side that hustling doesn't: finding ways to do things with far less resources that it would be normally required.
Essentially, scrappy is, IMHO, finding shortcuts and detours to avoid an obstacle. Hustling feels more like beating down that obstacle until it gets out of the way.
But that's all semantics, and therefore my personal opinion. I've always heard "scrappy" as a positive thing, and "hustling" as something either ambiguous or just plain bad.
