Suoinegni, I watched the Sheik Video instead because most of us...err Marth-users know that this particular Marth ditto is a match-up that usually throws out all conventional tools Marth has at his disposal and usually focuses on a defensive ground game. Therefore, critiquing that means most just critique a fraction of your playstyle.
So I watched Sheik and you face off with hopes for some aggressive action to wake me up from my half-slumber (and to hopefully see more of your air-game):
You missed like...a lot of F-airs. Considering your aerial game seems to be currently synonymous with F-air, that's kinda a bad thing. You had trouble punishing that Sheik even though that Sheik had little but roll, grab, charge needles, smashing, some aerials, and maybe some other stuff.
You had a good number of opportunities to punish the Sheik's smashing. You overused Shield Breaker, which while I admit that I don't use enough, you use a good number, except with little account of whether or not it'll benefit you.
You tried too hard to use Usmash to punish Sheik. First off, while Usmash was buffed from Melee, it's still not good enough for you to rush in and Usmash Sheik. Because you used it so often, it became harder for you to achieve vertical kills. To be honest, that whole match seemed to be won only because Sheik screwed up her recovery so often.
You had the same problem as me long ago in March and wanted to shieldgrab everything that hits your shield. That doesn't work with Marth. His range is not ROB's range, or Dedede's range (I would want to say it's as bad as the Ice Climber's range). He can't control a match off of mostly grabs like in Melee, or like the two I mentioned above. Out of a shield, you should punish with Dolphin Slash if your foe is rushing at you mercilessly, or Dancing Blade.
So yeah, your punishing game probably could be better. Maybe you never fought Sheik's before, or maybe you were completely apathetic, but you shielded a lot, but didn't really follow up.
Ah, and unless you completely miss, it's best to completely finish Dancing Blade. Lag may have screwed you here, but I saw a lot of unfinished ones even though you had Sheik right where you wanted her. Also, don't generally finish off with the upward slash unless you know you'll hit with it. I generally make the third hit upward too if I want to end with them up in the air because the third hit raises them ever so slightly for the 4th Umove. I didn't see much of your aerial punishment game, and was hoping you'll be able to pull off the upward Dancing Blade to possibly chain into something greater.
On the last stock, I noticed Sheik became much more aggressive. There was a particular moment where you tried to punish with Fsmash, but you could have gone with Counter and pushed Sheik away to give you some room.
I guess like what Emblem Lord told me, work on your responses, or your reactive play. Proactive play comes later, I guess when you shape up your responses to be more refined (which, by the way, I'm still pretty bad on).
Hey, since we both have Marths that need some fine-tuning, can you make it to this weekend's Waba monthly?:
http://smashboards.com/showthread.php?t=160978
It's on June 21st (Brawl), 22nd is for Melee (which I will not be attending because I haven't played that game in ages, and my mind can't split between two different Smash games). Err come early and let's play (mostly non-ditto matches).
