The difference between DVD-R and +R was just a pissing contest over which company got the deal. DVD-R standard came out in 1997, developed by Pioneer. DVD+R was developed by Phillips and Sony and was not an official format until 2008, so yeah. Salty Sony and their format wars. +R had some extra features and are considered more reliable because of that but it's all low level and not readily apparent to the user.
Ultimately the manufacturers of CD/DVD-RW drives just added in whatever firmware code needed to deal with all the DVD R standards and just deal with it that way since the optical hardware was the same.
That brings us to the HD-DVD and BluRay differences. While they use a similar optical wavelength, the structure of the coating containing the lands and pits is chemically different making BluRay able to hold slightly more data overall. Then it came to marketing and Microsoft, who backed HD-DVD hard, did not also own a movie studio AND a video game console.
TL;DR : DVD-R and +R exists cuz drive manufacturers made it compatible. HD-DVD died and BluRay lived cuz movie studios, and Sony.
Nice comment, thanks!
Microsoft had the Xbox by that time, and they chose to not include HD-DVD in the 360. It was an external drive.
And Toshiba was the big pusher of HD-DVD. Microsoft was meh about HD-DVD because it wasn't one of their ideas.
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