Mejor vs. más bueno
In Spanish, while both mejor and más bueno can relate to the concept of better, they are not interchangeable. Mejor is the standard and most common word for better or best, whereas más bueno has more specific and limited uses, often related to moral character or kindness.
Mejor
A2This is the direct comparative and superlative form of bueno (good). It is the most common and versatile word for better or best and is used to compare quality, skill, or state of being, or to express a preference.
Este café es mejor que el de la otra cafetería.
(This coffee is better than the one from the other coffee shop.)
Lionel Messi es el mejor jugador del mundo.
(Lionel Messi is the best player in the world.)
Después de la siesta, me siento mucho mejor.
(After the nap, I feel much better.)
Ella cocina mejor que su hermano.
(She cooks better than her brother.)
Lo mejor es que lleguemos temprano.
(The best thing is for us to arrive early.)
Mi coche viejo era bueno, pero este es mejor.
(My old car was good, but this one is better.)
Más bueno
B1This phrase is used in more specific contexts. Its primary meaning is kinder or more good-hearted when describing a person's character. It can also be used colloquially to mean tastier for food, or in some regions, more attractive for a person. It can also imply that someone has become better behaved.
Desde que tiene un perro, mi vecino es más bueno.
(Since he got a dog, my neighbor is kinder.)
Intenta ser más bueno con tus compañeros de clase.
(Try to be nicer to your classmates.)
El santo de la historia era más bueno que nadie.
(The saint in the story was more good-hearted than anyone.)
El pastel de mi abuela está bueno, pero el de mi tía está más bueno.
(My grandmother's cake is good, but my aunt's is tastier.)
Mi hijo era travieso, pero ahora es más bueno.
(My son was naughty, but now he is better behaved.)
Summary
In summary, use mejor as the default word for better or best when comparing quality, ability, or general preference. Use más bueno primarily when you want to specifically say someone is kinder or more good-hearted. While más bueno can be used for food, mejor or más rico are often more common. When in doubt, mejor is almost always the correct choice.