As a hairstylist I have found that men prefer women having long hair as opposed to women having short hair. Men also don't find clipper cuts or hairstyles where women have any part of their heads shaven very attractive.
This is a very subjecive question that really depends on the guy. Some men love short hair because it's easy to run your hand thru without mussing it. Other men perfer long locks that cascade and look very feminine. Your best bet is to find a cut that makes you look your best.
