Don't worry about it -- you're new, nobody expects you to know everything about the site yet.
I think this is a difficult topic for people because, while it IS a legitimate one that I think SHOULD be discusssed and that shouldn't hurt people's feelings, it often does. Not only that, but potential new members visit this site all the time, and since they aren't Greek yet they often take whatever they hear about Greek life as gospel. Some girls hear Kappa is great so they decide that's the only group they want to rush -- even if Kappa is tiny at their school or they don't fit in with the Kappas at all.
You can do a search for "best sorority" or "best fraternity" or something along those lines, and I'm sure lots of posts will come up -- you can always check out old posts for ideas.