When choosing a DVD writer, make sure it's physically compatible with the media you want to read and write. The good news is that virtually all players and burners sold today are designed to read mass-produced (or replicated) DVD-ROM and DVD-Video discs, as well as data and video content recorded on ±R and ±RW media. And despite some manufacturers' claims, equivalent dash and plus formats are virtually interchangeable from a user's perspective; neither offers a clear advantage in speed, functionality, media cost, or compatibility with third-party players. Further simplifying your buying decision is the fact that most rewriters sold today can now burn all four types of discs.

There are still isolated cases in which a disc that is recorded in one device won't play in another. Certain brands, speeds, and even lots of media can be incompatible with specific drives, an issue that arises most often with older hardware and higher-speed media. It's hard to predict when problems will occur, but when one does, your best bet is to experiment with different media speeds and brands until you find the combination that works most reliably with your drive the one format not based on the original DVD-ROM specification is DVD-RAM, which is rooted in the phase-change dual technology used in removable-media backup devices from the 1990s. While R and RW media closely mimic the structure of replicated DVD media, DVD-RAM employs radically different random-access data-storage and retrieval mechanisms that have more in common with hard drives than DVD-Video discs. Because it requires a different wavelength laser than other DVD formats, RAM media cannot be recognized by any player or rewriter that isn't explicitly designed to support it. It does include features more suitable for archiving critical data, such as hardware-defect management (which automatically compensates for flaws in a disc's surface) and the ability to record a disc up to 100,000 times—100 times as much as DVD±RW. DVD-RAM discs can be purchased with or without protective cartridges (although not all RAM drives can accept cartridge media) and are the only type of rewritable DVD media available with recordable surfaces on both sides.

Despite all this, DVD-RAM drives are far less popular in this country than DVD-Video models, and only a small number of consumer-electronics devices (mostly manufactured by Panasonic) support the format. The problem is that most people think of DVD as a video-storage medium and are content to use far cheaper R and RW media for occasional casual data backup. DVD-RAM discs' 4.37GB/side capacity is too small to make them a good choice for more demanding full-system backups, and although the format does offer superior data-integrity features, those features reduce the already relatively slow data-transfer rate. Nonetheless, DVD-RAM remains a fashionable choice in niche markets like the library, video-security, and medical-records industries, and it has even been used as a real-time storage medium in camcorders.