It is the most common question at the counter, and most answers online are either marketing copy or a chemistry lecture. Here is the practical version — in one sentence, then with the reasoning.
The rule of thumb
PLA if the part sits indoors, does not get warm and mainly has to look good. PETG as soon as moisture, chemicals, impact or heat are involved.
Put differently: anything that lives in a car, a dishwasher or outdoors is not a PLA part.
The temperature difference matters most
PLA softens from about 55 degrees. That sounds like a lot but is not: a car in the sun easily reaches 70 degrees on the dashboard. A phone mount in PLA sags after the first summer day — by far the most common failure we see.
PETG holds to about 70 degrees. That is enough for the car, the boiler room and parts that lie in the sun. Anyone needing more moves to ASA (95 degrees, plus UV resistance) or PA (100 degrees).
How they behave when they break
PLA is stiff and brittle. It takes high loads — and when it gives, it snaps without warning. On a form study that does not matter; on a bracket above your head it does.
PETG is tough. It bends before it breaks and takes impacts far better. Clips, hinges and anything with play therefore belong in PETG.
Where PLA is clearly better
- Dimensional accuracy: PLA barely shrinks, PETG a little more. On a gauge or a drilling template that is the decisive point.
- Surface: PLA prints cleaner, crisper, with less stringing. For appearance models and form studies it is the better choice.
- Fine detail: lettering, small pins, thin walls — PLA reproduces them more accurately.
- Odour: PLA barely smells while printing. On an overnight short run that is an argument.
And the others?
ASA is the outdoor material: UV resistant, weatherproof, sandable and paintable. A garden-equipment part in PETG goes brittle after two years, one in ASA does not. TPU is rubber-like — gaskets, dampers, equipment feet. PA (nylon) is the material for gears and plain bearings: very tough and abrasion resistant. PA-CF comes in when it has to be stiff and light.
You do not have to decide
Tell us where the part sits, what it carries and how hot it gets there — we take care of the material choice. The full list with heat resistance, properties and typical use is on the 3D printing page.