None. As a rule earbuds and headphones give you a poor idea of what a mix really sounds like, esp in the details and reverb. Decent speakers are better in almost every instance.
That said, there is someone here (maybe Phasys) who has been positive about some custom in-ear thingees that are pretty high end (and expensive). But I still don't thinking mixing on them could be a good idea.
Maybe if you then take your computer to somewhere there is a monitoring setup to fix the errors.