If the used balls are sold as “refurbished” you have to be careful. Some companies repaint that adds weight and hides flaws. Some have even been found to change the brand name after painting. Those issues will greatly impact performance.

I saw a video from one of the YouTube golf guys (Shiels I think?) where he tested the performance of refurbished vs. new Prov1s. He actually cut some in half to confirm the refurbished were the real thing (they were). On a lunch monitor the refurbished balls significantly underperformed the new Prov1s. His conclusion was the paint in the refurbished balls was the problem.

I agree with the concern over "refurbished" or repainted balls. However, I have had a good experience with 5A/mint "found" golf balls. Those are different from the refurbished or repainted balls. But I would not buy any lower level other than 5A/mint or equivalent.

Agree. I think refurbished balls are terrible.

I'm more curious about the 5A mint "found" balls (that aren't water logged!), that don't have scratches or nicks.

I would agree new is always better. You never know how long a ball sat in water or what condition it was In before being refurbished. If you care about your game enough to play a tour ball the small price difference is not worth the diminished performance

For whatever grading they use for “gently used” recycled balls, the vast majority of these recycled balls come from water hazards. The weight can vary beyond Titleist and even USGA limits. I buy new Titleist balls knowing that the lack of performance is on me.
Just know the recycled balls may not perform the same from ball to ball.

Interesting note Acushnet bought PG Golf ball recycling in 2018, they sell the Reload branded balls and sell direct through Lost golf balls.com So they might be a more reliable ball.