FermZilla vs KegMenter

Visibility

An underrated advantage of the clear vessel

Being able to see inside a fermenter is more useful than it sounds, especially for a brewer still building intuition. You can see the krausen form and fall, which tells you where you are in the fermentation without opening anything. You can see the trub layer drop and judge when a cold crash has done its work. And when something has gone wrong, you can often see that too -- a pellicle, an unexpectedly thin krausen, a fermentation that never really got going.

In an opaque stainless vessel all of that is inference. You compensate with instruments: a hydrometer sample, or a floating bluetooth hydrometer reporting gravity continuously. That is arguably better data, and it is an additional purchase.

Durability

And what 'consumable' really means

PET scratches. Not dramatically, and not from use, but from cleaning -- and a scratched interior holds soil in a groove that sanitizer contact time cannot reach. That is a genuine infection risk rather than a cosmetic complaint, which is why plastic vessels have a finite life measured in years.

Manage it and you get a long time out of one: soak with a non-caustic alkaline wash rather than scrubbing, never use an abrasive, rinse immediately after transfer before the krausen ring dries, and retire the vessel when the interior stops looking clear.

Stainless has none of this. It takes caustic, it takes a brush if you must, and it does not degrade. The reason not to buy stainless is price and the reason not to buy plastic is lifespan, and those are the two halves of the same decision -- stainless vs plastic fermenters works through it properly.