I'm looking for a phrase that would be roughly equivalent to the English "Quality vs. Quantity." Is there any catchy Italian phrase for this meaning?
If you mean Quality is better than Quantity, then I would use
La qualità è più importante della quantità
as in here.
I can't think of any idiomatic expression or anything catchier than that.
EDIT: if you mean the comparison between the two (I'm envisioning the case when you're doing a presentation and you want to talk about pros and cons), then the English expression will be perfectly understood, especially in a business environment. And used within an Italian sentence, unfortunately.
"Chi più spende meno spende" is an Italian proverb, but it is a very loose translation, suitable when you want to focus only on quality.
Literally it means "If you spend more, you spend less", meaning that the expensive high quality is an investment (for example, I buy cheap plastic shoes that I have to replace in 1 month, but you buy quality shoes 10X more expensive that will last for years).
EDIT: it's equivalent to "You get what you pay for"