The difference in sound quality between the rooms at the party must have been from the sound system. An mp3 is 128 - 192 kbits/s. A cd in a shop is about 320 kbits/s. A vinyl is literally infinitely better as it is a continual wave. I think the argument between decks and cdjs is a tricky one. on the one hand cdj's you can loop and mess about with the tunes more but i think the reason why many djs (including myself) are still drawn to vinyl is the actualy feel and romantic qualities of vinyl. Thats just my take on it anyway.