Choosing by what the part does
Most material questions answer themselves once you say what the part is for. The honest short version is below.
PLA
Stiff, cheap, dimensionally accurate and easy to print well. Best surface finish of the filaments. Softens around 60 degrees, so it is wrong for anything that sits in a car or near heat, and it becomes brittle outdoors over time.
Use it for display pieces, prototypes, models and indoor parts that do not take load.
PETG
The default for functional parts. Handles UV, moisture and impact far better than PLA, flexes rather than shattering, and holds up outdoors for years. Slightly less crisp on fine detail and more prone to stringing, both of which are manageable with a tuned profile.
Use it for outdoor fittings, brackets, enclosures, replacement parts and anything that will be used rather than looked at.
ABS
Tolerates heat well and can be vapour smoothed to a glossy finish. It warps readily while printing and needs an enclosure, which makes it more expensive to run reliably.
Use it where operating temperature genuinely rules out PETG.
TPU
Flexible and very tough. Prints slowly and does not suit fine detail, but nothing else gives you a part that bends repeatedly without failing.
Use it for gaskets, grips, bumpers, straps and protective feet.
Resin
Layer heights to 0.025 mm and a surface that usually needs no sanding. Harder but more brittle than filament, and standard resins degrade in sunlight.
Use it for miniatures, masters, jewellery patterns and presentation models. Do not use it for parts that take load. See resin 3D printing.
Still not sure
Describe what the part does, where it lives and what would count as failure. That is enough for us to recommend one, and the recommendation comes with the quote.