When to use “lieber” or “besser”?

Question

I have these sentences (with the correct choice boldfaced):

Das T-Shirt gefällt mir besser/lieber als die Blume.
Ich mag besser/lieber Orangensaft als Cola.
Mir schmeckt das Brot besser/lieber als das Brot in meinem Heimatland

I know the correct answers, but only because I’m German. How do I formulate a rule to explain this to a language learner?

Answer 1

Johnl's answer is saying everything: You'll have to find out if the verb you are using is using the adjective/adverb "gern(e)" or "gut".

Many sentences can be formed with both words:

Ich spiele gut/gerne Fußball.

In this case "gut" means: "well". (So you can do something well.)

And "gerne" (or "gern") means: You like to do this.

So one of the sentences means that you can play football well, and the other one means that you like to play football.

Now let's look at the first two sentences from your examples:

Mir schmeckt das Brot gut.
Das T-Shirt gefällt mir gut.

The subjects in these sentences are the bread and the T-Shirt. The bread is doing something: It tastes. And it is tasting well. But the bread does not like to do something. So "gern" cannot be used here.

Note that the word "gefallen" works differently than the word "to like" in English: Just like "to taste" the physical object is the subject in the sentence and the person who likes something is the (dative) object.

So according to English grammar the person is doing something with the T-Shirt (to like) while according to German grammar the T-Shirt is doing something (gefallen).

Now let's look at your third example:

Ich mag lieber Orangensaft.

In this example the word "gern(e)" is not used in the same way as in the examples above:

It is not an adverb which describes the verb!

In the sentence a fixed expression ("etwas gerne mögen") is used. You have to take a look into the dictionary to find out that the expression is not "etwas gut mögen" but "etwas gerne mögen". Sorry.

And finally we can have a look at mach's example:

Ich finde Orangensaft gut.

The verb "finden" has two different meanings. In this case it means: "To think that something is somehow."

The sentence using the verb "finden" is formed with an adjective describing the object, not with an adverb describing the verb:

Ich finde den Orangensaft gut.
("Gut" describes the substantive "Orangensaft" here, not the verb "finden".)
Der Orangensaft schmeckt gut.
("Gut" describes the verb "schmecken" here.)

Answer 2

besser ist die Steigerung von gut, lieber ist die Steigerung von gern. Daran sollte man direkt sehen, dass besser in (1) und (3) auch die richtige Lösung ist:

Das T-Shirt gefällt mir gut (nicht: gern). Das T-Shirt gefällt mir besser [als die Blume].

Mir schmeckt das Brot gut (nicht: gern). Mir schmeckt das Brot besser [als das Brot in meinem Heimatland].

Aber in (2):

Ich mag Orangensaft gern (nicht: gut). Ich mag Orangensaft lieber [als Cola].

Answer 3

This is an interesting observation. I guess at the bottom of this might be two different conceptualizations about qualities:

0. Preliminary note: Parties involved

Let me first lay out the parties involved. Like that, I can more easily describe the two different conceptualizations about qualities. There are two parties involved when we talk about qualities:

1. The party that possesses or is ascribed the quality. Prototypically, this is an inanimate party, though it need not be. For sake of convenience, I will call this party the “thing”, but keeping the quotes for signalizing that it need not be a thing.
2. The party that perceives or ascribes the quality. Prototypically, this is an animate party, though it need not be. For sake of convenience, I will call this party the “person”, but keeping the quotes for signalizing that it need not be a person.

1. First conceptualization: Passively experiencing a quality

In the first conceptualization, the quality is inherent to the “thing”. The “person” passively experiences the quality. On the grammatical level, this can manifest by the “thing” occupying the subject role (nominative case) and the “person” occupying an object role (dative or accusative case), which is unusual since it prototypically is the “person” who acts as subject:

Das Brot (nom.) schmeckt mir (dat.) gut.

Das blaue T-Shirt (nom.) gefällt mir (dat.) besser als das gelbe.

Der Orangensaft (nom.) dünkt mich (acc.) gut.

2. Second conceptualization: Actively ascribing a quality

In the second conceptualization, it is the “person” who actively ascribes the quality to the “thing”. On the grammatical level, this can manifest by the “person” occupying the subject role (nominative case) and the “thing” occupying the object role (accusative case):

Ich (nom.) mag Orangensaft (acc.) gern.

Ich (nom.) habe den Sommer (acc.) lieber als den Winter.

On the etymological level, both «lieb» and «gern» are related to emotional activities, cf. lieben and begehren or the etymologically related English verb to yearn.

At a first glance, the following case looks as if it were a counterexample:

Ich (nom.) finde den Orangensaft (acc.) gut.

However, when we look at the semantics of the verb, we see that it is not a counterexample after all: the act of finding a quality is not an active ascription of a quality. Instead, the quality is inherent to the “thing” and the “person” merely finds the quality, so this is rather a case of the first conceptualization in spite of the grammatical structure.

Answer 4

'lieber' expresses a preference
'besser' expresses a comparison

Note the first example here "Das T-Shirt gefällt mir besser als die Blume" doesn't contradict this: the preference is already implicit in 'gefällt', all that remains is the comparison