Well, I'm quite a fan of Sony but I don't think they have a chance in this one.
Nintendo has always dominated the handheld market and no doubt will continue to with their new release. This is about as bad as Microsoft stepping into the console battle. All they really did with that was take a computer turn it sideways and call it a console. I'm pretty sure all the games on it are even out for computer so I don't see the point in making it.

Anyway, the DS will probably take the win in this one. (Althought I won't be buying either, more of a console guy myself.)