Well vinyl is a uncompressed source, a single sound would probably not have a noticeable difference compared to a mp3 file, but if you build a whole track from mp3 samples it sometimes sound flat.
I only sample vinyl but im no purist, i love the adventure of diggin for records and it helps me find shit i wouldnt discover on the internet.
Do you basically.
Im a MPC guy so im not 100% on the sample-chain thats optimal for a software man but someone else will hopefully fill you in on that.