Spherical or Conical stylus. The tip of the needle is a small sphere (like the ball on a ball-point pen). This shape is very easy to manufacture. A record groove is "V" shaped, with the sides perpendicular to each other. The "ball" of a spherical stylus contacts the groove in two tiny spots. This places a ton of pressure on those areas, thus promoting record wear. On the plus, since the "ball" shape cannot reach the bottom of the groove, it masks some of the surface noise from worn records (pops, clicks, etc.)
Elliptical stylus. The tip is elliptical (egg-shaped). This allows the needle to rest deeper in the groove, allowing it to replicate the finer high-frequency modulations (higher frequency response than spherical needles). In addition, the "egg" shape allows the needle to contact a larger percentage of the groove walls. This distributes the tracking force over a larger area, reducing record wear.
Please see http://needleexpress.com/faq.htm for detailed images. How does this apply to us DJ's? Elliptical Stylii - PLUSES I baby my records. An elliptical stylus on a properly-adjusted cartridge mated with a good carbon-fiber record brush will extend the life of your record collection (as compared to spherical), yield a higher frequency response, and track incredibly-well while being played in a forward direction. Records that would skip while being played on a spherical stylus usually will not experience those same skips on an elliptical stylus. MINUSES Dust. You NEED to use a record brush. Vinyl heats up to 300 degrees Fahrenheight momentarily as the stylus passes through the grooves. Elliptical stylus dig very deep in the groove, bringing dust, smoke, etc to the surface. Since the vinyl deforms under normal playing, it's important to prevent dust from getting trapped in the groove (and baked onto the stylus). The other downside to elliptical styli is the fact that they shouldn't be used for scratching. While they will track like a champ, they'll eat the crap out of your vinyl (both resulting from that large contact area).
Spherical Stylii - PLUSES Easy to find. Cheaper than their elliptical counterparts. They won't wear your records as much during intense scratching/backcueing. Rugged. Good if your collection is beat-up and old. MINUSES Reduced dynamic range. Not as cool. Don't track as well. They will wear your records more during normal playback.
Conclusion - Here's what I do. Keep in mind that I'm a pretty anal DJ (ask Andrew). -For home use, I use Ortofon Concordes with yellow Nightclub Elliptical styli. It's the best setup for cd production and recording. Greatest dynamic range and high tracking ability. -At gigs, I bring Ortofon OM cartridges mounted on Technics headshells. I will use blue DJ spherical cartridges if the environment is uncontrolled (ie. house party, or club or rave with poor DJ booth/turntable isolation). I'll use the yellow Nightclub Elliptical styli if the booth is well isolated or if it's a top-notch sound system. I recommend the Ortofon OM headshell models if you're going to play out. They are meant to be mounted on a headshell, thus eliminating the common contact problem that people have with the Ortofon Concordes (ie, a channel going out). Reminder. I recommend the Ortofon cartridges for most mixing applications. They are designed to be a little flexible with regards to proper adjustment (cause most DJ's don't set their needles up correctly). If you choose to buy Ortofons, keep in mind that the ONLY difference between models is the stylus. Slap a Nightclub stylus on a Blue DJ, and you have a Nightclub. The OM versions are the way to go. Less sexy, but they perform more consistently. If you're looking for lower-than-catalog prices on Ortofons, contact my supplier, David Dittmer