National Comparison

Sorority is for the four years you are in college. The only thing that matters about your sorority after college is the friends you made and the experiences you had. Nobody else in your college after-life will care what sorority you were in, or even if you were in a sorority. No particular set of letters will help you socially or professionally, or gain you respect or admiration in any way. There are alumnae from every sorority all over the place to connect with. You are not going to get an automatic advantage or disadvantage in the adult world for your sorority, that's entirely up to you as a person.

nationally, phi mu is very weak. zeta is only slightly stronger. the only real strength either of these houses have is in the south, but anywhere else they're very weak.
anywhere else, your most relevant houses will be the party school trifecta (APhi, Pi Phi, DG) or the older money powers (Theta, ChiO, Kappa)

Northeastern states have very strong chapters of ASA, AST and SDT

I’m going to put this in the same category as grades. Are grades important? Yes. Do they determine where you pledge? No. Nobody goes through rush with these criteria as their main selection reason. It’s where you feel at home and the girls in the house that help a pnm decide. No is right. After college nobody is going to care what sorority you were in and it rarely matters “in the real world”. So my advice is to go through rush with an open mind and pick where YOU want to go back for the reasons important to you. Don’t worry about the rest.

at other SEC schools PM and DG are lower tier

No one cares except old ladies who live to pretend they are important at a national convention or people who are in a weak house at Bama "but but but my house is top 8 states away" (where they would never get a bid anyway).

The only thing that matters is matching with a sisterhood where you fit at the school you actually attend.