Antojarse is of the olvidarse/perderse group of reflexive verbs where the subject is at fault. The subject of the sentence is the desire. It is an overwhelming, enveloping, or even possibly a far-fetched way to express a desire. It is a desire that occurs, that affects, that comes over you.
When it's cold, you often feel like putting on a jacket.
When you're sick, you crave something like an aspirin to help.
When you're starving; famished, you feel like eating.
- Se me antoja manejar mi carro
- Se me antoja tocar la guitarra.
- Se me antoja cocinar
- Se me antoja una cerveza
- Se me antojan encurtidos metidos en helado.
gana is a desire, literally. So it isn't any kind of idiom when you slap
tener in front of it. So translated, it is literally
I have desires to.... It's a bit more personal, it's more long-lived, it's a personal goal.
I want to go to Disneyland! --indicates a set goal.
- Tengo ganas de hacer paracaídas.
- Tengo ganas de ver esa película.
- Tengo ganas de bailar
- Tengo ganas de irme de aquí
Ultimately though, they are more or less interchangeable.