The thing to keep in mind here is that Anime Conventions as a whole are a hell of a lot YOUNGER than Sci-fi/Fantasy cons.
Let's put it this way, in the simplest terms possible:
Sci-fi/fantasy cons have longer established traditions and less cons throughout the nation. Therefore it will appear to both people within and without that circuit to see their competition as stronger merely because there are more established costumers and less cons for them all to go to. Also, convention directors tend to have a long established love and appreciation for costumes from their fandoms, and like to attract talented costumers to their conventions.
Anime Conventions are still relatively new, but have spread like a disease across the country. The talent is still young and spread thin, so it would appear the competition is less. That and it's apparent to me that most Anime convention directors have little knowledge or respect for costuming, so don't care enough to emphasize it in their programming
This is the best way to explain the differences. As Anime cons grow and most fledgling cons die off, you will start to see them evolve more into the state Sci-fi/Fantasy cons are at now.
Evil Kimba and Danzikumaru - The Gear Project cosplaylist (tentative):
San Japan = Germany and Prussia (Axis Powers Hetalia), Ellis and Bill (Left 4 Dead), Wriggle Nightbuf (Touhou Project)
Cosplay Co-Director of:
in San Antonio, TX