Question

Saying "you're a fantastic person" rather than "you spent your whole weekend helping me move" is an example of

Answer 1

It's an example of emotive language.

Emotive language is the deliberate word choice that is used to evoke emotion (usually to influence).
Ideas can be expressed non-emotively: "you spent your whole weekend helping me move". Or they can be expressed in a more  positive or negative way: "you're a fantastic person"