PLA, PETG or resin: how I actually pick

Almost every material question I get is phrased as "which one is best", and it doesn't have an answer. What it has is a decision tree, and it's three questions long.

Question one: how hot does it get?

PLA softens around 60°C. That sounds high until you remember a parked car in July hits 70°C on the dashboard, and a windowsill in direct sun gets closer than you'd think. If the piece is going anywhere near either, it's PETG and the conversation is over.

This is the single most common way a print fails after it leaves me, and it's the one nobody expects. A bust that sat perfectly on a shelf for a year will sag in an afternoon on a car dash.

Question two: does anyone touch it?

Pieces that get handled daily — hooks, trays, clips, stands, planters — take small impacts constantly. PETG flexes and comes back. PLA is stiffer, which means it takes the same hit by cracking instead.

Display pieces don't have this problem, which is why PLA is fine for plaques, lithophanes and boxes even though it's the more brittle plastic.

Question three: how small is the detail?

Filament comes out of a 0.4mm nozzle. Below about 0.8mm of feature width there is nothing a filament printer can do for you, no matter how fine the layers are. Faces, chainmail, fabric folds, insignia — that's resin territory, at 0.03mm layers, and it isn't close.

The cost is brittleness and UV sensitivity. A resin bust on a shelf out of direct sun will outlive all of us. The same bust on a sunny windowsill will yellow noticeably inside a year.

The short version

• Somewhere hot, or handled every day → PETG
• On a shelf, needs a clean surface → PLA
• Small and detailed → resin, and keep it out of the sun
• Outdoors → PETG, in shade, and accept it won't last forever

If you're unsure, tell me where the piece is going when you order and I'll pick. It costs the same either way and it's the difference between a piece that lasts a decade and one that lasts a summer.