i normally sample wavs (after i convert them from mp3). I'm just now gettin' in vinyl though, 'cause you can find stuff that either few or no ppl have ever heard of before. Plus records are cheap!
.... and for me, i use CDEX, so techinically when i record a track from vinyl to my PC, it's an MP3, then i convert it to WAV and begin the chop shop
All in all, i like both formats, but vinyl is the key that opens alot more doors than MP3.