Refund on oyster card

https://www.visitlondon.com/traveller-information/getting-around-london/oyster-faqs/how-to-get-a-refund

when in doubt go to the horse's mouth.

TfL do everything to do with Oysters.

Go to https://tfl.gov.uk/fares/refunds-and-replacements?intcmp=54643 "No Longer Needed" is at the top right of the page, then follow either "Pay as You Go Oyster Card" or "Visitor Oyster Card" depending on which Oyster you wish to cash out.

Note that unless it is a very old Oyster you won't get your initial deposit (£5 or £7) back - if there is any chance of you returning you may decide to hold onto it for a future trip, they are good forever or whatever forever means these days, or give or sell to another person travelling to London.

If you are at home realize that any refund will be in Pounds Sterling, not dollars.

I was watching a well known travel vlogger yesterday and she was adamant, do not under any circumstances get an Oyster card. Tap and go was her rule since there's a daily cap. Same for visitors passes.

And her opinion on which to use is paramount to anybody else’s why?

Personal preference. Some prefer to use the Oyster Card so as to potentially not lose a credit card. The cap is the cap whichever one uses.

I prefer to use an oyster card that I've had for many years so that I am not constantly pulling out a credit card. I don't want to risk losing a credit card.

If I had never previously bought an oyster card I would likely use a credit card.

I disagree with anyone who categorically says to never use an oyster card.