Its has to do with Booktype.
DVD-r is the only industry standard for recorded media. Most will play this
DVD-rom is a standard commercial format. All players should play this
DVD+r is a unrecognized standard in the industry and can be recorded as DVD-r, DVD-rom and DVD+r, which is why the industry does not like it. Some players will play DVD+r disks
Phillips DVD Players will play anything !! Sony will play almost nothing. Was your BR a Sony?
Nero will automatically set the book type to DVD-rom if you use DVD+r disks. If you use DVD-r it can change it because it is a set book type.
Image Burn you have to set it manually.
But remember you only change booktype on a DVD+r disk
Also quality of the disk is very important. Cheep dye can cause all kinds of problems. Phillips are crap. Verbatim, and RiDATA tend to have the best quality. But there are whole web site about DVD burning
Burning at slower speeds is a myth, unless of course you have a P-III but when your burning or transcoding do not touch your computer !!!!!!!!