Opinions on wine and champagne yeast?

I've heard a lot of people say they've used champagne yeasts to attempt to fix stuck fermentations and for other reasons. I've never used it before, but my basic, shoddy logic and instincts tell me this isn't the best choice.

When we're talking about a stuck fermentation, we're usually talking about unhealthy yeast that have given up after they mostly ate the simplest sugars in a wort. So at the time of the stuck fermentation, you're looking at a wort with less than simple sugars, right? Probably a lot of di and tri-saccharides and less single sugars?

While I'm sure that various wine yeasts have various abilities to ferment some of these higher sugars, I feel like it's worth noting that grape must is mostly (entirely?) simple sugars - fructose and glucose. So I'm guessing these yeasts aren't particularly adapted to fermenting the diverse sugars found in wort?

I know it's tempting when you see the "up to 18%ABV" on the champagne pack, but surely alcohol tolerance isn't the most important factor when it comes to a thorough fermentation.

It seems like lager yeasts are some of the best choices for stuck fermentations, or finishing off a big beer so it has a low FG. Don't lager strains have a better ability to ferment more complex sugars?

Thoughts on any of this?

That has certainly always been my experience, though lager yeasts at warm temperatures produce their own crop of problems. I would certainly go this route over champagne yeast, though I'd probably try pitching a neutral dry yeast first, like US-05.

I believe that lager yeasts can break down maltotriose, whereas most (all?) ale yeasts can't.

I don't think either does a good job for fixing stuck fermentation, but I have used both back when I bottle conditioned to bottle condition high gravity beers where the abv of the beer exceeded the yeast tolerance. But, your logic would indicate this would work as when bottle conditioning you are adding simple sugars back to the wort which the wine or champagne yeast eats up just fine and because of the alcohol tolerance it is able to finish its desired job: carbonating the beer.

If this is why you are using it, I personally think the wine yeast gave a more neutral flavor. The champagne yeast through some pineapple/cidery flavors. These calmed down over time. I've got a 3 year old English Barleywine that came in at 16% (yes, we were seeing how strong we could make it) that bottle conditioned lovely with champagne yeast.

Adding more yeast is never the answer to a stuck fermentation. A champagne yeast could tolerate more alcohol than an ale yeast, but most stuck fermentations won't happen because an ale's alcohol went over 12%. Even then, it is one thing for a yeast to enter a wort and ferment it from the start. It is another to dump a packet of dry yeast into a wort that already has 10+% alcohol, no oxygen, and probably little FAN.