Technically, vinyl can only give you about 60db S/N exclusive of the pre-amp (although different vinyls these days provide somewhat better that that), and CDs at least 95db+, so CDs will always be quieter. A properly designed phono pre will, itself, be quieter then the record, so you shouldn't have any additive noise.
However, with a lot of the newer turntables these days having internal ADC/DAC systems to get you that USB connection that can't be switched out of the way to get your a direct out RCA feed, then your S/N is going to be based on the turntable's electronics, not the vinyl.