Most of the good stuff has been covered, but a couple of comments might be helpful.

The "modern" CD from the name brand suppliers is usually coated, over the recording layer and the "soft" plastic top sheet, with a coat of harder lacquer to protect the top surface. While there is some additional resistance to scratches, the main purpose of the coating is to reduce gas (and liquid) permeability of the surface. Some makers claim a degree of UV protection from the topcoat, but I haven't found reliable info on how prevalent, or how effective, it is.

Even with this lacquer coat, a disk may delaminate if moisture/gas contaminants seep in from the edges, so some manufactures put an "edge coat" on to seal the rim.

While the top coat is a relatively small increment in the manufacturing cost, it it often omitted on "no-name bulk" CDs, even if they're made by one of the major producers. The edge seal is "very expensive" to apply, so is almost never present on the unbranded bulk ones. Whether this makes a difference probably depends on how you handle and store your disks.

The house brand blanks will normally be tested to verify that some certain "maximum acceptable error rate" is not exceeded, and will likely also be subjected to at least some handling and durability tests on a lot by lot basis. The "bulk" disks, to keep cost down, will have a higher "acceptable error rate," and are unlikely to go through any significant lot test for other characteristics. This means that the reflection layer may be thinner, a cheaper dye layer may be used, and other unknown cost reduction "skimps" may be used.

Providing very cheap disks for those who need them is certainly a valuable service, and the providers need not be denigrated as giving us "defective" products; but it must be understood that these bulk disks present greater "unknowns," and hence are questionable for "important work."

Reports from data disk manufactureres and users indicate that "name brand" disks can be expected to preserve data for 50 years or more, if reasonably stored. Accelerated life testing by manufacturers makes this estimate quite credible. We'll know for sure in about 50 years. (That's about the same "archive life" as for stuff laserjet printed on typical office paper.) Bulk disks usually should not be considered good for more than a couple of years, and exposure to direct sunlight may erase some of them in a few hours. Some of these disks may retain useful data for very long times, but there is no assured life for them, and no significant testing to make any estimate other than "short" believable.

Regarding compatibility with auto and other portable devices, one select group heavily into audio play from CDs and CD-Rs makes the claim that the main cause of failure to play in mobile equipment is off-center labels. Most auto and other portable players run a small felt pad or two on the outer 1/8 inch or so of the disk to keep it from bouncing around. If an applied label is even slightly off center, this can cause speed fluctuations that the player can't follow. Even a screen print label that's off can apparently cause the problem, and it's seen fairly frequently in "commercial" discount audio disks sold in truck stops where these guys hang out.

I haven't seen technical info to back this claim, but these truckers are "pretty pro" and may know what they're talking about. If you've had problems, an unlabelled disk (at least without a paper label) from the same lot that wouldn't play might be worth a try.

John