X yori mazui / X yori oishii

"X yori mazui" / "X yori oishii"

which one means that X is preferred? i'm a bit iffy on the use of "yori." some sources say it simply means "than," some say "more than," and some say otherwise, so i'm quite lost.

If you are comparing X and Y, for example,

- Y wa X yori mazui = Y is less tasty than X.
- Y wa X yori oishii = Y is tastier than X.

Thanks! I'd received an odd compliment from a friend ("まー　君よりまずいと思うけど　＾。−"), and I wanted to know if I'd interpreted it correctly.

ありがとうね！