Verified answer

Tienen el mismo significado aunque en algunos contextos se utiliza mas frecuentemente una que la otra:

She looked at me as if / as though I were mad.

Take an umbrella. It looks as if / as though it’s going to rain.

I can’t understand why she’s so keen on him. It’s not as if / as though he’s good-looking or anything.

Al menos en USA es mas comun utilizar as if.

Agrego una acotación interesante para ampliar tu conocimiento:

In spoken informal English, particularly American English, we sometimes substitute like for as if and as though:

-She looked at me like I was stupid.

-It looks like it’s gonna rain.

as if como si, ni que as though como si fuera like analogo, comparable, parecido, similar eso es el significado pero debes tener en cuenta donde lo vas a utilizar en la oracion o al traducir casi siempre el latino trata de traducir palabra por plabra y no el concepto de la oracion. cualquier cosa estamos para ayudarte

No hay ninguna diferencia entre as if y as though

1. as if / as though = para decir lo que algo nos parece

she looks as if / as though she has had an argument.

(Ella tiene aspecto de haber tenido una discusión.)

It sounds as if / as though someone is crying.

(Suena como si alguien estuviera llorando.)

He was talking as if / as though he was sick.

(Hablaba como si estuviera enfermo.)

En estilo informal, norteamericano sobre todo, estas mismas frases se pueden hacer con "like":

she looks like she has had an argument.

It sounds like someone is crying.

He was talking like he was sick.^

NINGUNA, AMBAS SIGNIFICAN LO MISMO

por lo que tengo entendido no hay ninguna diferencia. saludos!