From the perspective of a
DJ, believe it or not, there are several reasons to choose
CDs over
vinyl.
The first reason is very important for a DJ playing on high-power sound systems. When you play records, you're taking a sharp needle, and dragging it across the physical representation of your music.
Repeatedly. Ever hear of a little thing called erosion? This leads to a degredation in quality of sound. This does not occur with CDs.
The second reason is the flexibility that DJing with CDs can offer.* When you DJ using vinyl, unless you happen to own a vinyl press, you are limited to using only what production companies have felt the need to press to vinyl. With CDs, as long as you can find a CD quality (not that compressed shit) copy of the track, you can always burn and play it. (With the permission of the artist, of course.) It also makes life much easier if you produce your own music.
Third, it is more accurate to beatmatch with CDs than it is with vinyl.
I felt a disturbance in the force. As if thousands of vinyl DJs cried out in pain, and were suddenly silenced.
Yes, I know that this is easily the most controversial point I'm making in this dialogue, but it's a debatable point. When you drag and brush a record on a vinyl turntable, the rate of change is subtly affected by several variables, including the size and drag of the hole in the middle of the record, the moisture and heat level of the slipmat, and many other variables, mostly having to do with the number of points of friction present when using vinyl. The same level of brushing or dragging can produce different results in the pitch change, a disadvantage that doesn't exist using CDs. This is a subtle advantage, but to a perfectionist like myself, it is a notable one.
Another reason that CDs *can* be better than vinyl is the wealth of options that are available with CD equipment that would be impossible to have on vinyl. With the advent of the Digital Vinyl series by Pioneer, DJs on this equipment can scratch or perform backspins with ease. There are CD players that come with built in samplers and looping functions, allowing the DJ many options in creatively cutting up and remixing music. The looping function in particular is completely infeasible to have on vinyl equipment. With the release of the CDJ-1000 CD player by Pioneer, suddenly the technological goodies available for CD DJing shot through the roof. This bad boy even comes with a memory card that you can use to preprogram cue points, loop points, and even use as a sampler. I defy *ANYONE* to to show me a vinyl turntable that can do this.
The best reason to choose to DJ CDs over vinyl, though, is really simple. Like the softlock says below: personal preference. Some people are very, very attached to the tactile aspect of using vinyl to DJ. For some people, this same thing would be a liability. If you prefer to deal with things in a tactile manner, vinyl would probably be best for you. However, if you prefer to deal with things as non-concrete, abstract concepts, CDs would probably be more your speed.
Lastly, I never, ever, once will ever have to pay to replace the cartridge on my equipment. Bwahaha.
I'm not saying that CDJ equipment is intrinsically better than vinyl. Far from it. Vinyl DJing is an important part of DJ culture, and I would never, ever want it to go away. For certain applications, vinyl is far superior to CDs. But for those with an open mind about what equipment will be best for them, there are just as many reasons to choose to DJ using CDs than with vinyl.
*Update: mkb has informed me of a product called Final Scratch that can be used to play Mp3s from computers using vinyl turntables. Odd, I know, but it is an extremely clever product. A cursory glance at Google, however, reveals a price tag of $500 for this setup, making it only viable for those people who are willing to spend an extra half a grand to either avoid the social stigma of DJing using CDs, or who are already set up and used to using vinyl. I, personally, would rather just spin CDs than spend a couple thousand extra dollars on equipment and a laptop so that I can rip and spin music on vinyl that I'll be buying on CD anyway, b/c it simply isn't available on vinyl, or for legal MP3 download. I'm just not that interested in following the status quo.