In the world of arcade games the word candy is used to identify Asian built JAMMA wired arcade machines that are made competely out of plastic and metal, and have absolutely no wood used in their construction at all.
They are called candy cabinets because of the resemblance of many of their components to shiny hard candy. This isn't just a nickname either, as the industry itself has adopted the word officially. My Japan built NeoGeo MVS cabinet has the word "candy" proudly adorning the marquee area permanently (below a window where you display the name of the game currently in the unit).
Overall candy cabinets are engineered and designed far better than normal American and Australian arcade cabinets. They are lighter, more difficult to damage, easier to service, and often have features that American machines just don't have.
There is one significant difference between standard American arcade cabinets and Japanese "candy" cabinets, that is the fact that candy cabinets are designed to be played by a seated player, while American cabinets assume a standing player. I will go over the other features below.
Candy cabinets almost always feature a whole lot of monitor. They are almost all monitor. My NeoGeo candy cabinet has a 29" monitor, while much larger American machines will have a 19" or 25" one. But, it doesn't just stop at big screens. Candy cabinets always have a late model monitor that has a remote adjustment board to make adjustments easy. Compare this to American machines which will often have a monitor in them that has been rebuilt several times over the past twenty years. I cannot count the number of newer machines I have owned that had old monitors in them. I personally think that the game operators pull the late model monitors out of their games before selling them off, and replace them with old ones that they had laying around.
You can usually rotate the monitor in a candy cabinet quite easily. Some of them are actually mounted on a big lazy susan which allows effortless rotation, while others require you to undo a few bolts and rotate. Compare this to American cabinets which have no standard at all for this.
Candy cabinets seem to be almost completed standardized when it comes to control panels. Every one that I have ever seen has two joysticks (usually Sanwa brand) and either 4 buttons or 7 buttons. The models that have 4 buttons will always have 3 plugged up button holes, which can be filled with the extra buttons to play the Capcom fighters, like Street Fighter 2. The ones with the 4 button layouts were often equipped with NeoGeo MVS hardware.
The actual quality of the controls is a bit lacking when compared to the joysticks and buttons that your local arcade might have, the controls on the candy cabinets tend to be almost all plastic, and the buttons do not have separate microswitches. When I first purchased my NeoGeo I had assumed that I would have to replace the controls with more heavy duty Wico joysticks and buttons, but I got used to the Japanese style controls almost instantly, and now have dropped plans for replacement controls.
Most candy cabinets have a large front door, which is where the PCB and JAMMA wiring harness is stored. They leave a huge area open for this, and I have a NeoGeo motherboard, a Uo Poko PCB, an X-Men PCB, and a Break Thru PCB mounted in mine and I still have plenty of room left inside.
Any other standard service related items can be accessed through the coin door, inside this door is the power switch, the knob to adjust the power supply, the service switches, and so on. Be aware that most of these cabinets only have a single coin acceptor, and some American JAMMA boards will expect two of them for two player mode.
Overall I would have to say that a candy cabinet is an excellent purchase if you are looking to buy an arcade game, but you don't want an older unreliable model. These can often be had on ebay, and can pe purchased from many different importers. They are usually sold without a JAMMA board inside, but those can be had one eBay for as little as $10.