SideFX's design was awesome, but there was nothing about it that related to Smash. These t-shirts can work as advertisements for the website. Even though the name of the website is almost a dead-giveaway, the design of SideFX's shirt doesn't show what the website is all about. Someone can look at Milktea's design and say, "Oh, look, it's Meta Knight! I love that guy. All Is Brawl.com, huh? Maybe I should check it out."
Personally, I was rooting for both Milktea's and J-Nav's designs because they showed some of the roster. I'm glad that Milktea was the winner of the whole thing.

Congrats Milktea.
Fweeee :3