This question comes up in pretty much every beginner forum thread, usually phrased as if there's a correct answer everyone else already knows. There isn't. Both materials make good beer. I've fermented in plastic buckets, glass carboys, and a PET carboy that a friend talked me into buying, and the differences are real but smaller than the debate makes them sound. Here's what actually matters.
Plastic buckets: the default for a reason
A food-grade plastic bucket fermenter is what most starter kits ship with, and that's not just a cost-cutting move. Buckets are light enough to carry full without thinking about it, they don't shatter if you set one down wrong on a tile floor, and the wide mouth makes cleaning and pitching yeast easy. Most come pre-drilled for a grommet and airlock, or you can drill one yourself in about two minutes.
The catch is that plastic scratches. Every time you scrub a bucket with a brush, you put fine scratches in the surface, and over months of repeated cleaning those scratches get deep enough that they can theoretically hold onto bacteria or wild yeast even after sanitizing. In practice this takes a long time to become a real problem, but it's the reason buckets aren't a forever purchase — most home brewers replace a bucket every 1 to 3 years of regular use rather than treating it like a one-time buy. At $10 to $15 a piece, that's a minor cost, but it's worth knowing going in so a scratched-up bucket doesn't surprise you later.
It helps to be specific about what "cosmetic" versus "a real problem" looks like. Hold the bucket up and look across the surface at an angle, not straight on — light-catching hairline marks from a soft sponge are cosmetic and don't hold onto anything a sanitizer can't reach. Run a clean fingernail slowly across the inside wall instead of just glancing at it: if it glides smoothly, the scratches are shallow. If your nail catches or stutters on an actual groove, that's deep enough to shelter bacteria below the reach of a surface wipe-down, and no amount of contact time fixes a groove sanitizer can't physically get into. A cloudy, frosted look across large areas of the plastic — not just a few scattered marks — is the other tell; that's the plastic breaking down. When either sign shows up, replace the bucket.
Glass carboys: no scratching, more fragility
Glass doesn't scratch under normal cleaning, doesn't absorb odors or stains the way plastic can over time, and it's genuinely satisfying to watch fermentation happen through clear glass — the krausen rising, the airlock bubbling, the beer slowly dropping bright. If you like watching your beer work, glass gives you that in a way an opaque bucket never will.
The tradeoffs are real, though. A full 5- or 6-gallon glass carboy is heavy, often 40+ pounds once filled, and it's the kind of heavy where dropping it doesn't just make a mess — it can turn into a genuine hazard with broken glass and beer everywhere. Glass can also crack from thermal shock if you move it between very different temperatures too fast, like pulling it out of a warm closet and setting it directly on a cold garage floor. And the narrow neck that gives glass its classic shape is the same reason it's harder to clean than a bucket. Getting a brush or your arm into a carboy neck to scrub off stuck-on trub is awkward, and a lot of brewers end up relying on carboy-cleaning tools or a soak-and-swirl approach instead of a straightforward scrub.
PET plastic carboys: the middle ground
PET carboys try to split the difference. They're shaped like glass carboys, so you get the same see-through view of fermentation, but they're plastic, so they're lighter and won't shatter if you drop one. They still scratch over time the way any plastic does, and they still have the narrow-neck cleaning issue that glass carboys have, so they don't erase every downside — they just trade "heavy and breakable" for "still scratches eventually." If the visual appeal of a carboy is what draws you but the weight and breakage risk of glass makes you nervous, PET is a reasonable answer.
Conical fermenters: worth it once, not worth it yet
Conical fermenters have a cone-shaped bottom with a valve, which lets you dump trub and dead yeast partway through fermentation and harvest yeast for reuse without opening the vessel at all. That's a genuinely useful feature once you're brewing often enough that yeast harvesting and fast turnaround start to matter. But conicals cost several times what a bucket or carboy costs, and for someone brewing a handful of batches a year, that valve is solving a problem you probably don't have yet. This is equipment to grow into, not to start with.
The harvesting itself is worth understanding, since it's the whole reason the shape exists. As fermentation finishes, dead yeast and boil sediment (trub) settle down and, thanks to the cone, funnel into the narrow point above the valve — a bucket or carboy's flat bottom spreads that same sediment thin instead, which is why you can't do this trick with them. A day or two after fermentation slows, you crack the valve to drain the thickest, darkest sludge first and dump it, then close it again. Once cleaner, cream-colored yeast settles into that same spot, you open the valve again and collect that layer into a sanitized jar — that's your harvested yeast, ready to pitch into a future batch, sometimes after a quick wash step. Doing this without a conical means opening the fermenter and scraping yeast off the bottom by hand, which is messier and riskier since you're breaking the seal to do it. For a brewer building up a rotation of batches, harvesting a clean pitch for free without breaking the seal is where a conical's cost starts paying for itself.
So which one should you actually buy
Start with a plastic bucket. It's the cheapest option, the most durable against the one accident that ruins your brew day — dropping it — and it's easy enough to clean that you'll actually do a thorough job every time, which matters more for your beer than the fermenter material does. None of the downsides of plastic show up on batch one, or batch ten, really.
Move to glass, PET, or a conical only when you have a specific reason pulling you there: you want to watch fermentation happen, you'd rather avoid plastic altogether even at the margin, or you're brewing frequently enough that easier yeast harvesting actually saves you time. Upgrading by default, before you've identified which of those reasons applies to you, just means spending more money for a fermenter that solves a problem you don't have.