I can't watch the video right now, but I can tell you that Mach3 will in some certain situations exceed the acceleration values, due to a bug (bugs?) in the trajectory planner. Most people never see this issue, but for some, it makes Mach3 unusable.
Mach4 should not have this issue at all, but I'm not sure how good or what state the CS Labs Mach4 plugin is in.