falcon gets comboed harder than marth by sheik? i'm no so sure.... sheik can tech chase falcon but doesn't auto combo from zero.
Falcon actually has the tools to bait and punish sheik in his speed and all of his hits lead into more hits. The problem with falcon in every match-up is getting the initial hit.
Marth however, relies on keeping people at tip length or farther. Most of the time, marth can swing his sword and get an another attack out before the punish arrives. Against sheik this is almost never the case thanks to dash attack and grab. Not to mention sheik can stay outside his sword and needle and marth has no option but to close the distance. When he does, she can slide forward and shield any attack (then grab->****) and spotdodge any grab. Marth has to rely on predicting dodges and rolls and then also work on punishing them consistantly (i have a hard time with this as marth, rolls are hard to punish when you have to tip or get cc->tilt->*****)
basically what i'm saying is, how bad falcon vs sheik is is exaggerated. If marth vs sheik is 60-40 then sheik vs falcon is 55-45 or less.