Most first spools are PLA or PETG, and the choice affects what you can make. This checklist uses the printer maker Prusa's public knowledge base, credited below, and applies it to a real filament seller.
1. Start with what the part is for
The Prusa Knowledge Base PLA page says the best use of PLA is for concept models, prototypes or low-wear toys. Its PETG page says PETG is used universally and is especially suitable for mechanical parts for both indoor and outdoor use.
2. Check the heat the part will see
Prusa notes that PLA does not resist high temperatures and gets soft and deforms above 60 °C. If the part will sit in a hot car or near a heater, PLA is the wrong pick. PETG is described as having good temperature resistance.
3. Check your printer and bed
Prusa recommends about 210 °C and a 60 °C bed for PLA, and says PLA does not require a heated bed. For PETG it recommends 230 to 240 °C and a bed of 85 to 90 °C, and says PETG requires a heated bed. Those are one maker's profiles, so check the spool's own range and your printer.
4. Expect different quirks
Prusa says PLA is not prone to significant warping, while PETG is prone to stringing and should not be printed on a smooth PEI sheet because adhesion can be too strong. A first-time printer may find PLA more forgiving.
5. Read the return terms before you stock up
Many sellers accept only unopened filament, so a spool that prints badly may not be returnable. Buy one spool first, check who pays return postage and whether the warranty covers print problems.
An example: checking a seller against the list
In our SUNLU review we applied these questions. The store lists 1 kg PLA from about $10 and PETG 2.0 at $12.99, but accepts only unopened filament for returns, charges the buyer return postage and showed no independent testing.
A note on the sources
Prusa Research is a printer maker that also sells its own filament, so its material guidance reflects its own printers and profiles. We wrote this article in our own words. Some links to brands on this site are affiliate links; see our affiliate disclosure.