I think it depends on your definition of winning. So far, the comments I've seen are mostly all craftmanship-based. That's great, if a craftsmanship award is your gig.
Now, if you're looking for a Best in Show, which is the award /cgl/ argues about the most when they argue, that's going to take at least both good craftmanship and a good skit.
From here, this is my opinion only. Your mileage may vary.
I say "at least" because sometimes, something with amazing craftmanship but only an OK skit will win, or you get an amazing skit but the costumes are just OK winning. This is typically where I've seen the most arguments arise.
And how might this happen? In terms of sheer numbers, it involves averages. If you max out your scores in craftmanship, you can usually afford to lose a few points in presentation and still have a chance to win because the high scores will pad the low ones. You can't totally fail the skit, but if you can provide something that the judges like, that's going to go a long way. Same goes the other way; if you have a fantastic presentation, but you're costumes are not elaborate, at least making sure that the finshing is clean, your fabrics are appropriate, and that you've taken some care in your work will certainly not hurt, and the judges typically will see that.
When you compete, the judges are your first priority to impress, because they are giving the scores. The only exception is where audience response counts towards the win.
