I think if you go back a month or so in this thread, somebody suggested that Cactuar thinks its 60-40 Marth, and then Cactuar responded with "wow I never said that/if I did that's horribly outdated."
It's definitely Marth =< Puff imo. You have no edgeguard vs automatic edgeguard, you have character who in actuality rivals Marths range with bair + aerial movement, Marth has no reliablie kill move that's reasonably safe, oh and Jiggs has a OHKO move that you need to constantly be wary of.
I think just as quickly as people want to point out that M2K's marth gets ***** by puff, people are just as dismissive in saying "oh m2k just played bad". Yea, ok, m2k playing bad is better than most everybody on their best day. Not to say its a horrible matchup for Marth, but to say that Marth actually is advantaged is completely out of the question imo.