Between two equally informative descriptions, shorter is better.
Between two equal-length descriptions, more informative is better.
Hype is right out. (If the other people would all like their website described the same way, it's hype.)
Focus on mentioning all the types of content that you have and another site might not. That will indicate what kind of things the editor should make sure and include in the review; since it's objective information and it's about the website, it's less likely to be trimmed.
And really, don't worry too much about the word count. If you just list what the website has, it probably won't go over thirty words after the editor has done the usual syntax-polishing. If you just boast about yourself or urge people to visit the site, it should get trimmed no matter how few words it is.