I disagree. I would say quantity over quality up to a certain degree. Doing two average quality sites doesn't take double the time than doing on quality site.
It's a concave function and today it's all about networking!
Having like 500 average blogs or spam blogs with less certain updates and only 10 "money maker" blogs which get supported by all their inbound links will make you a lot more money than concentrating on 5 "quality blogs" where you do 5 updates a day with the very best sponsor content and all the like.

It depends a lot of course, ifyou wanna have sucess with a paysite in a very competitive market then it's about the quality. If you're doing free sites, galleries, blogs and TGP's it's all about quantity!