I'm going to go a different way. I would say take the first opportunity you are offered. Every sorority offers a similar experience so I don't think it's as critically important to be exposed to every one. If you have an opportunity to informal rush and you have a connection, I'd go for it. If you go through informal and you're feeling really meh about your options, then by all means wait and go through formal as a sophomore.
But just like boys, you don't have to have dated every one to know you like THIS one.
My opinion
