I am going to take a guess and say whatever actions are available to Marth at the time. For example, in dash forward you can shield, Dtilt, Dash Attack, short hop, shield, etc. Each carries different benefits, faults, and traits.
In dashing forward is Marth going to JC grab, Dtilt, aerial, stop in place, dash back, or other options? Dash back might threaten to outrun any attempt to be attacked and dash right back to punish ending lag of said attack at Marth. But, is dashing back going to really carry any threat if Marth has very little room to dash back?