When I went through recruitment, we had 7 sororities on my campus. For the first two days of recruitment, you went to all 7, and after that second day there was mutual cutting. I liked that opportunity to have two days in all of the houses-- it gave you more of a chance to meet more people.
My chapter never participated in an informal recruitment event, and I didn't really even know what that was until I became an adviser for another chapter. I am all in favor of informal! At my university, the fraternity recruitment consisted of a kick-off orientation event, and then you could hang out at any house/s you wanted to go to. They'd either offer you a bid at some point or give you the hint to try another chapter. Once a guy got a bid, he hung out at the tent and helped recruit.
I like some aspects of that idea, too.
Informal recruitment is just less stressful and is more flexible. However, I have worked with chapters whose Greek Adviser is not in tune with the best interests of those universities, and no one is at total (or even close) and the quotas each fall don't help the chapters in getting to total. So they have to have informal recruitment all year. It is a strain to get initated women to come out for the events, and a strain to find PNMs-- at an academically challenging campus, there are classes and test and graduate schools/internship preparation and part time jobs, in addition to trying to hold it together with extracurriculars. Having the manpower to hold a COR event and getting PNM's there can be very draining, especially when so much effort is put forth and only 4 PNMs show up!
Just my 2 cents. Everyone has some great perspectives to share on this thread. It is wonderful to hear so many personal experiences and everyone's great ideas!