Paying everything up front vs. 0% installments
On one hand, 0% interest payment plans do make more financial sense because a dollar today is worth more than a dollar in the future.
On the other hand, psychologically, you experience that “purchasing” emotion every month the money leaves your bank account, which is usually negative.
My approach is to take the 0% interest payment plan on stuff I have to pay for (e.g. a hospital bill), but pay the entire amount ip front otherwise and save myself multiple bank account dings.