Modern compound bows generally come with a choice of 4 different types - or styles - of cam systems (Single, Hybrid, Binary, or Twin). While they all accomplish a similar mechanical goal, they each have a unique set of attributes and respective advantages and disadvantages. While the technical subtleties and respective merits of the various cam systems could be debated in perpetuity, in the real world there is an obvious performance parity among them all - especially now that string fiber technology has improved. This isn't to say that they all cam systems perform exactly the same. They certainly don't. But to say that one cam style really offers a crucial field-advantage over another would be something of a stretch today.
Often described as a Solocam or One Cam, the single cam system features a round idler wheel on the top of the bow and an elliptical shaped power-cam on the bottom. The single cam is generally quieter and easier to maintain than traditional twin cam systems, since there is no need for cam synchronization. However, single cam systems generally do not offer straight and level nock travel (though the technical debate continues), which can make some single-cam bows troublesome to tune. Of course, all single cams aren't created equal. There are good ones and bad ones. Some are very fast and aggressive, others are quite smooth and silky. Some offer easy adjustability and convenient let-off choices, others don't. But most single cams do offer reasonable accuracy and a good solid stop at full draw. Overall, the smoothness and reliability of the single cam is well respected. The single cam is still a very popular choice on compound bows today.
The hybrid cam system features two asymmetrically elliptical cams: a control cam on the top, and a power cam on the bottom. The system is rigged with a single split-harness, a control cable, and a main string. Though originally invented and marketed by Darton Archery as the C/P/S Cam System, Hoyt's introduction of the Cam & 1/2 (a variation of the original C/P/S System) in 2003 brought hybrid systems into the limelight. Hybrid cams claim to offer the benefits of straight and level nock travel, like a properly-tuned twin-cam bow, but without the timing and synchronization issues. Indeed, hybrid cams require less maintenance than traditional twin cams, but it's probably a technical stretch to say that hybrid cams are maintenance free. They too need to be oriented (timed) properly for best overall efficiency and performance. There are several hybrid cam models available which are impressively fast and quiet, rivaling the best of the single cam bows.
Introduced by Bowtech Archery as a new concept for 2005, the Binary cam is a modified 3-groove twin-cam system that slaves the top and bottom cams to each other, rather than to the bow's limbs. Unlike single and hybrid systems, there was no split-harness on a binary system - just two "cam-to-cam" control cables. So the cams didn't pull on the opposing limbs - they pulled only on the opposing cams. This created a "free-floating" system which allowed the cams to automatically equalize any imbalances in the limb deflections or string and control cable lengths. So technically, this self-correcting cam system had no timing or synchronization issues and would achieve perfectly straight and level nock travel at all times. The only drawback was that without split harnesses to equalize the limb tips, slaved cams were subject to cam lean - a problem which Bowtech seemed to resolve in subsequent versions. Since 2005, many bow companies have utilized this style cam - albeit under other names and cosmetic variations. But make no mistake, Binary Cams have become a huge force in the industry. They're fast - really fast - and they're easy to tune. Ironically, the latest version of the Binary Cam, the "Overdrive Binary," moved the "free-floating" functions to an elliptical gear drive assembly inside the cam, and returned to the use of a split-buss cable to totally nullify the cam lean. So the most advanced version of the Binary Cam looks like a complicated Twin Cam ... but it's not.
A Twin Cam system is sometimes described as a Two Cam or a Dual Cam. The Twin Cam system features two perfectly symmetrical round wheels or elliptical cams on each end of the bow. When properly synchronized, Twin Cam systems offer excellent nock travel, accuracy, and overall speed. However, Twin Cams can require more maintenance and service to stay in top shooting condition. But thanks to today's crop of advanced no-creep string fibers, they are becoming increasingly easier to maintain. Many hardcore competition shooters are quite loyal to the twin cam concept. And it's probably worth noting that the Twin Cam bow is dramatically more popular outside of the US and Canada, where there is less advertising to hype the single and hybrid systems. Aside from maintenance issues, the only true disadvantage to twin cams is the tendency for increased noise (compared to typical single and hybrid cams). Nonetheless, the Twin Cam is still the cam system of choice for many serious shooters. Twin Cams are also very popular choice for youth bows.