what even makes a sorority a higher tier?

I will get real with you. What makes a sorority top tier: campus involvement, great GPAs and a strong presence within the greek community. But: attractiveness plays a huge role in tiers, and so does money. The rich girls can travel and make the sorority marketing look great. They have the resources to get every t-shirt, go to every event and then some. And are able to afford clothing and what not to look nice. Spoil their little's. MOST importantly is sisterhood. Example: Alpha Phi has a lot of great qualities mentioned above but have a TERRIBLE sisterhood. KD does not have a lot of qualities above and are one of the top because they have a super strong sisterhood. Shady-pi (ADPI) is probably the rudest, most stuck up sorority on campus but they yes have a great sisterhood with one another, Keep to eachother. Just trying to be real.

we don't have houses so tiers aren't really that relevant, when you rush just make sure to find the sorority who you click the most with to get the most out of greek life & don't pay attention to this site

TBH, sororities have tiers just like high school has social tiers. When you go through recruitment, look beyond the facade of your initial impressions. These girls will be your best friends through college and beyond. Look around, especially before pref night, the girls you pref with will likely be your new sisters. Are these girls who you want for life-long friends. Tiers change, your sisters are forever.