For me it's quality every time. If someone writes 30 hubs in 30 days and much of it ends up as very poor quality then I think they have wasted their time. Having said that, I'm sure there are some Hubbers who can really rise to the challenge and produce quality as well as quantity!
But I think the sad fact is - and I agree with Faceless39 - there are many hubs written in about, I reckon, 5 or 10 minutes and they are awful! They are boring and are crappy and I don't read them. For me, people who produce low quality hubs of this nature couldn't care less about writing, entertaining or informing their readers all they care about is money.