From what I understand, Mizzou is a bit more competitive than KU when it comes to sororities. That means it's quite competitive. If you have good grades and activities and can get recommendations for each house, then you should go for it. A strong system like that has a lot of campus connections to offer you, and should be filled with plenty of quality people who have a lot of fun.
And definitely check out the threads mentioned above.
PS, one of my really good friends is rushing at Mizzou this year. I'm so excited for her!
Mizzou has a very competitive recruitment. There are 14 houses and each take a new member class of around 60-75. Last year about 1200 participated in recruitment. Grades are very important as well as activities. Sororities are not for everyone, but greek life at Mizzou is very rewarding. It was a huge part of my life and now a huge part of my own children's lives there. Good luck with your decision.