One thing that's physically different out there in the BD-R world is "HTL" vs. "LTH" media. The original Blu-ray disc is "HTL" (High to Low), based on a non-organic technology. The disc starts out highly reflective ("H") and the laser burns the non-reflective pits ("L"). The original technology used a layer of copper and a layer of silicon. When heated by the laser, the two materials combine, forming the low-reflectance part. This is a very reliable technology (in theory, much longer lasting than the organic dyes used in CD-R and DVD-R), and it's also stable in sunlight.
However, everyone's after cost savings, so some time after the BD-R was introduced, some manufacturers introduced the LTH BD-R. This uses the same kind of organic dyes used on DVDs (more or less... some tweaks are needed to change the optical response); the disc starts out low reflectance, and the laser changes the dye layer to expose the reflecting layer (this is the opposite of the way HTL, CD, and DVD work, but the technology is similar to that of DVD). LTH discs have the same vulnerabilities as DVD. Older BD-R writers won't support LTH without a firmware upgrade.