RCS vs. XLR inputs

I'm using KRK Rokit 8 RPG2's for my studio monitors.
Which input you rate is better? The RCS (unbalanced) input from my sound cards S/PDIF out, or XLR (balanced)
Iv'e heard that RCA, because its Digital its really quiet in comparison!

If anybody can shed some light about it, id'e be grateful
Clint
 
The RCA's on the back of your monitors aren't digital, they're unbalanced analogue, so they wont work with the SPDIF output of your sound card. Use the XLR or TRS inputs.