Re: dsPIC33FJ and SPI bus SD card communication
The Sony might be near end-of-life as well - eventually taking a lot of time for error correction.
While you might not hear data errors, error correction is really important when it comes to data storage.
So the Sony card could well be the better product - just not appropriate for your application.
PEBKAC / EBKAC / POBCAK / PICNIC (eventually see en.wikipedia.org)