From my perspective, it depends on what your current goals/goals for the project are.
Quantity I see as being a better focus when your main goals are growth and learning. When you're trying to learn or master a skill, it seems like just going at it and getting a large quantity of work done is often more valuable than spending a wealth of time on each particular instance. I'd rather doodle 100 gestures to get a better feel for them than spend 5 hours working on a single one. Or 500 hands or 10 comic pages, or whatever. Of course the idea is that you're not just mindlessly pushing out quantity- in order for this approach to be worth it you do have to be striving for improvement at the same time.
It seems like most comics kind of fit on this side of the spectrum regardless of whether it leans towards "quantity" or "quality" relative to other comics: no matter if you do a page every other day, or once a week, or even once a month or whatever, the constant production and quantity of pages and panels that you push out is a great learning tool. Quantity also works in the creator's favor on many hosting sites due to how these algorithms typically work. Tapas for example, getting on fresh at least once a day helps more people see your work, the more people that see (and enjoy) your work, the more subs, likes, and comments you get, and the more of those you get the easier it is to break onto the trending and popular lists, which help even more people see your work.
Quality on the other end of the spectrum, I see as being more appropriate when your goal isn't so much to try to rapidly grow and improve, but rather when you're just looking to put your current best foot forward and make the best product you can make. Commissions, for example, often fall into this category. If someone is paying you for a piece of art, you typically want to produce the best thing you can to make the client happy. But not just those, for a comic project if you're not particularly concerned with the release pacing for readers, or just really want to make something super beautiful, the focusing on quality for those is good too!
But like the caveat either way is that you ideally don't want to go all in on 1 way or the other. Again, if you mindlessly pump out content without pushing yourself at the same time, you wont improve much despite the quantity. And if your quality is too low, it doesn't matter how often you post.
And similarly, if you care at all about building a reader base with your comic as you're uploading it, there's some sort of lower limit on the quantity that you can produce before you should either consider: completing the project up front before beginning to post so you can control the release schedule to something more pleasant for the readers (once a week instead of once every 3 months when you finish your masterpiece pages, as an extreme example lol)
^ and also this. Very much this xD Ideally (or after a lot of practice) you should strive to get to a point where you can have both. Even if "both" is both aspects at like 70% or 80% (instead of both at 100% or whatever). Relatively snappy turnaround with good or great quality is the goal