Most people meet this comparison the wrong way round. They read that ABS is the tougher, more professional, more industrial plastic, buy a spool, and discover that their open-frame printer cannot finish a part larger than a coffee mug without it peeling off the plate. The material question comes second. The first question is what machine you own.
The gate you have to clear first
ABS needs a chamber that stays warm. Not a heated chamber necessarily — a passive enclosure that keeps the air around the part from being stirred by the room is usually enough — but something. Without it, the top of a growing part cools while its base stays welded to a 90 to 110 °C bed, and the resulting internal stress either lifts the corners or splits the part along a layer line halfway up.
PLA has no such requirement. It runs on a cold plate if you insist, tolerates a fan pointed straight at it, and does not care whether the window is open.
So the decision tree is short:
- Open-frame printer, no enclosure. Print PLA, or PETG if you need more than PLA gives. ABS is not a realistic option and no amount of brim, glue or bed temperature makes it one on a large part.
- Enclosed printer, ventilated room. Now the comparison is genuinely open and the rest of this page applies.
- Enclosed printer, unventilated bedroom or office. Read the ventilation section before you buy anything.
The strength assumption runs backwards
The single most common reason people switch to ABS is that they want a stronger part, and on the numbers that swap is a downgrade. PLA's tensile strength is stored here at 45 to 65 MPa; ABS at 30 to 45 MPa. Whatever ABS is for, it is not for making a part harder to pull apart.
What ABS has is a different failure character. PLA is stiff and it snaps; ABS yields, deforms and absorbs energy before it gives up. A bracket that is loaded steadily and never dropped is better in PLA. A bracket that gets knocked, levered or over-tightened is better in ABS, and the number that tells you so is impact resistance, which no filament spool prints on its label.
There is also a fabrication difference that rarely appears in strength tables. ABS takes a tapped thread, accepts a self-tapping screw without splitting, and can be solvent-welded into an assembly that behaves as one piece. PLA cracks around a tapped hole and glues indifferently. If your part is going to be screwed into, that is a real argument.
What warping costs, in millimetres
Take a 200 mm bracket. At the top of ABS's stored contraction range — 0.8% — it finishes at 198.4 mm, and modelling it to land on size means drawing it at 201.6129 mm, a correction of 1.6129 mm. The same bracket in PLA at the top of its range finishes at 199 mm and needs a 1.005 mm correction. Both of those are top-of-range figures. The bottom of each band asks for materially less, which is why a bracket that fitted last month can miss this month on the same spool in a colder room — so bracket your own part between the two ends of the range in the shrinkage calculator rather than trusting a single number.
Half a millimetre of difference across 200 mm does not sound like much, and as a dimensional error it is not. The problem is that contraction does not happen politely at the end — it happens continuously, layer by layer, while the part is still anchored to the plate, and the force it generates has to go somewhere. On a large flat ABS footprint it goes into lifting the corners. That is why the practical answer to ABS warping is never "compensate for it" and always "keep the part warm while it prints", and why warping is overwhelmingly an ABS problem and only occasionally a PLA one.
What ABS actually buys
Three things, and it is worth being precise about them because two of the three are frequently claimed for the wrong reasons.
Heat. ABS holds shape to 88–100 °C against PLA's 52–60 °C. This is the honest headline. A part that lives on a car dashboard, near a heat vent, inside a 3D printer's own enclosure, or in an attic in summer is a genuine ABS job.
Acetone. ABS dissolves in acetone vapour, which turns a layered surface into a glossy one and seals it against water ingress. Nothing in the PLA family does this, and no amount of sanding produces the same result on a complex curve. If your part is cosmetic and complex, vapour smoothing is a capability, not a trick.
Machinability. It drills, taps, sands and files like a plastic rather than like a brittle ceramic. Anyone who post-processes parts by hand notices this within one afternoon.
Ventilation is a constraint, not a forum superstition
Printing ABS releases styrene and fine particulate. An enclosure contains it while the lid is shut and releases it in one go when you open the door, which is exactly when your face is closest to the machine. If the printer lives in a room you sleep, work or eat in, either duct the enclosure outside, run a filtered extraction, or choose a material that does not create the problem.
This is where ASA and PETG earn their popularity. ASA against ABS is nearly the same plastic with far better ultraviolet behaviour, and it emits similarly, so it is not the answer to fumes. PETG against ABS is, for most of what people actually print.
The recommendation, stated plainly
If you own an open-frame machine, this comparison has one answer and it is PLA — or PETG when PLA is not enough, which is more often than PLA fans admit and less often than ABS fans claim.
If you own an enclosed machine, use ABS when the part must survive heat, be vapour-smoothed, or be tapped and screwed into. Use PLA for everything you would rather have arrive dimensionally correct on the first attempt, because it will.
And if you are choosing between them for a part that is neither hot nor cosmetic nor threaded, you are choosing between a material that costs you nothing in effort and one that costs you an enclosure, a ventilation plan and a higher failure rate. The cost of a failed print is the term that decides this, and it is almost never the price per kilogram — the two materials sit within a few dollars of each other at similar quality.