Monsieurs et Mesdames,
A call to order on definitions. The expressions "large winery", "medium-sized wineries", "small wineries", "boutique wineries" and "garagiste wineries" relate to one and only one thing - the physical size of the winery - that is to say, the number of winse produced. The terminology has nothing whatever in common with the quality of the wines produced.
Defining a boutique or garagiste winery by the individual attention it gives to vine location, trellising methods and winemaker's intents or desires has no meaning and that for two reasons:
(a) small wineries have a limited number of vineyards/grapes from which to choose. Because of that you can be fairly assured that if only 30 barrels of wine are harvested, almost all of those grapes will find their way into the "top level" wines of the winery and that almost regardless of quality. Small wineries have far fewer options for final blends (even in a 100% varietal wine) than large.
(b) at least some of the very best wineries pay an enormous amount of attention to what is happening in the vineyard and thus in separating/selecting grapes for premium wines, mid-level blends and lower-level blends. More than that, because a large winery will have far more grapes from which to choose, they are in an ideal position to make wines at different levels. Boutique/garagiste wineries do not have that ability.
A related point - there is absolutely no guarantee in predicting the quality of the wines of wineries in any of these categories. That depends largely on the vines, the winery, the winemakers and yes, the owners of the winery who often set the philosophy. And, of course, experience over time. Let us keep in mind for example that when Chateau Le Pin started up they did so in a garage (literally) and until they released their wines were considered little more than a joke in Bordeaux. The same might be said of an Israeli winery in the city of Tsfat (Sefad) which started out earning a reputation as a joke and has managed to maintain that reputation for nearly a decade.
On a thoroughly personal (albeit also professional) basis, I have fairly well abandoned using the terms "garagiste", "boutique", etc in favor of "very small", "small", "medium-sized", "large" and if one likes even "gigantic". As said earlier, that describes nothing but the size of the winery and says nothing whatever about the quality of their wines.
Finally, I cannot help but wonder if the use of terms such as garagiste and boutique have not have not been abused and in the name of "romance". Something akin perhaps to the use of terms such as: Selected, Reserve, Special Reserve, Royal Reserve....?