To outside observers, the idea that a humble 5-gallon (19-liter) glass jug could inspire heated debate might seem a touch preposterous. But many homebrewers form very strong opinions regarding the secondary fermentor. Some claim that the secondary is almost always necessary, while others brag about how many months their 1.112 (specific gravity) barleywine has been sitting on the yeast.
First of all, even though we all say it, secondary fermentation isn’t really the right term. Little to no fermentation actually takes place in secondary, which is why I often go out of my way to refer to this phase as conditioning, maturation, or lagering (in the case of the eponymous cold-fermented styles). Whatever you call it, secondary is simply the vessel to which beer is racked away from the yeast and trub that remain after primary fermentation is complete.
I am nothing if not moderate, so here are the arguments for and against, presented so you can decide which camp you fall into.