just a girls opinion

I can't really answer that cause I'm not personally a part of any of them. I will say that of all the big name fraternities the only ones I've really seen having a strong brotherhood are SigEp and SAE.
KA Fiji and Beta are very cliquey. Delt has a lot of drama. Sigma Chi and Pike don't know half their own actives.
Kappa Sig and Sigma Nu both seem to have pretty good brotherhoods but that may be because they're smaller

I can't speak for all fraternities but I can give a general idea.
Top: SigEp has the strongest brotherhood for top tier followed by SAE. KA and Fiji are both cliquey high school heros but at least KA has decent brotherhood.
Mid: Nobody here really has good brotherhood. Sigma Chi probably has the strongest out of mid tier but it's only mediocre. Delt is too busy with infighting for brotherhood and Pike gives out too many bids to even have a chance at good brotherhood. I really don't know about Beta, but I don't think it's great.
Low: The chapters are smaller but they have great brotherhood. Kappa Sig is the exception because they have good brotherhood and a large chapter. Sigma Nu also has good brotherhood and Deke is okay.

Delt has a pretty sub-par sense of brotherhood from what I've heard. Fights at parties, arguments on NG, guys sleeping with each other's girlfriends, word spreads.

Pike and Sigma Chi are all about the numbers and are focused on expansion so I don't think they even really care about brotherhood

Anyone else I'm sure is solid