33girl, DITTO!
The main thing is fitting with the members where He would like to end up. They will be His Brothers for a long time.
Greek Organizations will fluctuate from year to year. Up now, but could be down next year.
Also, I suggest that He check out through National Web Sites to get a picture of what each represents.
Chapters, where and how many.
In a growth pattern or just circling.
Chaity events.
Check other chapters web sites to see what they are doing Fraternaly.
Dang, it is so much easier to do now than in the Good Old days of rushing.
Back when we did formal Rush, Guys went to 3 Houses a night. Six Greek Organizations in two nights was just a cattle call!
Good luck to Him and Hope He finds a Fraternity that works for Him and Them.