Both sound like a good deal, but it really depends what you want. I personally prefer the S710a because it had an amazing QVGA screen that looks brilliant, and it also has a good camera (much better then the W600). I also find the W600 to be too small. However the W600 has a good music player (but less storage then then S710a) and the S710a can easily be described as bulky. But yes, to answer your questions, $100 for an S710a is a very good deal (make sure you ask them what condition it is in though, because is a very low price).