IMHO they have rather different demands on the player.
SCH is more about mindless APM much of which can be done on autopilot. Embrace spam is the big one here of course, but working for that 45 second aetherflow is a pretty similar story.
AST has a much lower work rate but demands more mental agility of the player with the somewhat unpredictable nature of cards. You can streamline it somewhat with flowchart style prioritisation but on the flipside, Sleeve Draw can be an absolute pig at times.