I buy music on vinyl too. But today's mixers are digital so when you plug in your turntable, sound is processed through a DSP at 24-bit 96kHz on mainstream club mixers (like the DJM-800) or 32-bit on high-end equipment. Many say that digital mixers sound better than analog ones but the truth is that records simply sound different, not better, it's an illusion.
As for MP3, I can just tell that OGG sampled at the same bit rate sound better than MP3. Too bad most portable music players/car radios don't support it.