Might depend on the country though. I grew up where credit unions were really common and just assumed they were the best. I had to switch to something else cause I moved across the country and my credit union was only on western Canada. While shopping around, I realized that the big Canadian banks were offering way more than my credit union ever was. Plus their website actually felt modern.

The first time I bought a car I secured financing through Capital One before I went to the dealership, and then once I found a car told the dealer I'd finance through them if they could beat my other lender's interest rate. They did, by like a quarter percent. Years later when I went to buy another car I got financing through a credit union instead, the rate was much lower than before, and the dealer couldn't beat it.

Well one disadvantage of credit unions is that you might not be able to get a debit card. Loan interest is usually way better though.