[userbinator]

It doesn't matter if the cereal I bought tastes good or bad, I'll always wonder if the other option would have been better. Until I taste the other cereal, I'm left questioning my decision, and being unhappy.

In this case you would probably be able to try the other option at some time in the future, so why would you be unhappy? I'd definitely do that, and probably alternate between the two if they seem equally good.