The Short Answer
Choose PLA for display models, concept prototypes, and any part that will not be exposed to heat or mechanical stress. Choose PETG when you need a functional part that is tougher, moisture-resistant, or potentially food-safe.
Printability
Both materials are considered "beginner-friendly," but PLA edges ahead. It prints at lower temperatures (190–220 °C vs 230–250 °C for PETG), adheres readily to most bed surfaces, and produces minimal warp. PETG is slightly more prone to stringing if retraction is not dialled in, but this is easily managed.
Strength & Toughness
Tensile strength is similar (~50 MPa for PLA, ~53 MPa for PETG), but the key difference is toughness. PETG has an elongation at break of ~130% vs ~6% for PLA. In practice, PLA snaps under sudden impact while PETG bends and absorbs the energy. For any functional part, PETG wins.
Heat Resistance
PLA softens at around 52–65 °C. Leave a PLA part on a car dashboard in the sun and it will deform. PETG holds its shape up to 70–80 °C - still not suitable for engine bays, but fine for most indoor and moderate outdoor applications.
When to Use Each
- PLA: Architecture models, concept prototypes, figurines, display parts, educational models
- PETG: Mechanical enclosures, snap-fit parts, outdoor fixtures, food-adjacent applications, structural brackets
If you are unsure, PETG is almost always the safer choice for functional parts - and the printability gap has narrowed considerably with modern slicers.