IMO the difference can be atributed to both better transport mechanism in the CDP-777 and the lack S/PDiF interface in the integrated player - eveything is in one box, so you do not have to encode the data and clock signals into S/PDiF (coaxial digital out) and then decode them back in the DAC. The S/PDiF interface is very prone to jitter, if the DAC and transport are not clock linked - and in case of Reimyo stuff, they aren't.
The digital part - BB1704 24-bit DACs and JVC Extended K2 processing - is the same in both.
The digital part - BB1704 24-bit DACs and JVC Extended K2 processing - is the same in both.