If it was my money (but, I know...it ain't), I'd go with the PSR-S910...well worth the bit more, and, as Gary has said above, no reliability issues whatsoever.

Plus, it uses the new style engine as in the Tyros3/4.

Personally, I found the S910 quite a substantial improvement sonically over the S900...the sound just had more punch and yet was sweeter as well.

Ian