A folder normally has one side of the coin exposed, this can cause uneven, undesirable toning. You also have to use quite a bit of force to put a coin in a folder this can lead to damage/fingerprints on the coin

Here is an example of an album: https://www.amazon.com/Dansco-Lincoln-Cent-Coin-Album/dp/B008RM326C/ref=sr_1_8?crid=22KWQ3YC3LQ7Q&keywords=Dansco+album&qid=1680546328&sprefix=dansco+album%2Caps%2C173&sr=8-8&ufe=app_do%3Aamzn1.fos.006c50ae-5d4c-4777-9bc0-4513d670b6bc

Compare this to a folder:

https://www.amazon.com/Lincoln-Cent-Folder-Whitman/dp/0794840043/ref=sr_1_1?crid=2CFIEG1VH2C58&keywords=lincoln+cents+folder&qid=1680546372&sprefix=lincoln+cents+folde%2Caps%2C102&sr=8-1