A search here for "quince" returned zero results, but that doesn't mean people haven't (or aren't) fermenting quince juice.
I'm fermenting a half gallon of quince as a substitute for real tannic cider apples in a British Cider recipe I'm brewing. The rest of the juice is from a few varieties of eating apples. Since this is sort of a test, I'm fermenting the quince separately from my three gallons of apples.
If it's a direct replacement for a bittersharp cider apple, I can use it to bitter up half the batch, and use tannic blend for the other half. The unfermented quince juice is awesomely tannic, with that black tea skritch way back on the tongue. I don't have any experience of juiced bitter cider apples, so I don't know if the quince is more or less tannic than a classic tannic cider apple.
My recipe is 40% sweet, 30% acidic, 30% bitter apples. My apple juice tastes like it's at the 40/30 ratio for sweet/acid, but I don't know if the quince juice will overpower the balance, or if cider apples are as tannic.