the touch pro from sprint has 512 mb of rom while the diamond only has 256. the ram size is the same at 288mb for both devices. thats why youre seeing the descrapencies in the two devices. hope that helps you out a bit.
if you wanna see for yourself here are the links to the htc site for sprint.
touch diamond
http://www.htc.com/us/product.aspx?id=62730
touch pro
http://www.htc.com/us/product.aspx?id=71536