The sound of all interfaces comes with the analog cicuitry, before and after the preamps and converters. Different components, even if passive, will lead to a different sound. It could be the difference of a capacitor that costs 79 cents rathern than 8 cents. You can be sure Prism doesn't skimp on anything.
MOTU 828mk3 also uses the PGA2500 chip, and those preamps are muddy and noisy as all getout.
