The difference is the 3G data networks that are supported by each phone. The C905a model uses the 3G frequencies used in the US and the C905 used in Europe. Either model will work for voice calls (same frequencies) in the US or Europe.
if anybody could explain me the difference between these two phone I would really appreciate it, am planning to buy one from this site, there is a difference in price so asking for an advice.
between Sony Ericsson C905
Sony Ericsson C905a
Thank you in advance.