If you are at a bigger school, the competition might be more cutthroat to get into ANY sorority.
However, at a smaller school, the composition of each sorority might be REALLY different and you might only be happy in one of them. You might not be able to get into that one for various reasons. And just because it is a smaller school and maybe not as prestigious a Greek system - don't think it is a cake walk & everyone who wants to pledge gets a bid. They don't.
The thing you should really focus on is chapter size - would you rather be in a sorority of 150 members or one of 40 members?
Good luck and congrats on your acceptances.