Heres the skinny:
DVD-R/DVD-RW
- The 'official' standard.
- First standard, first commercial burners supported this standard
- Example - Pioneer DVR-A03 - DVR-A05
- Not gaurenteed to work in set top (VCR style) DVD players
- Not gaurenteed to work in PC DVD-ROM drives (but DVD-R will work in the majority of cases). Not sure on wether the disc must be finalised.
DVD+R/DVD+RW
- Newer standard, claims to support more set top boxes
- IIRC faster to finalise a +RW compared to a -RW
- Example - Phillips DVD burners are all +R/+RW
- Not gaurenteed to work in set top (VCR style) DVD players
- Not gaurenteed to work in PC DVD-ROM drives (but DVD-R will work in the majority of cases). Not sure on wether the disc must be finalised.
- Not recognised by the DVD Forum as DVDs, so dont carry DVD logo
DVD-RAM
- THE format for archiving and storing data / backups
- Not readable by any set tops boxes
- Not readable by any DVD-ROM drives
- Not readable by DVD+RW drives
- 9.4 GB per disk
- Much longer shelf life than either other two
- Much more expensive per disk
Generally, DVD-R/RW drives can also be DVD-RAM drives, but DVD+RW cannot.
Compatibility with other players/hardware is not jsut a function of the DVD format, but also of the disk used. 4x burners generally will not burn at 4x except with very specific disks, and finding the right disks is troublesome.
The only multiformat I am aware of (two in fact) are the Sony drives DRU500AX and its older brother (DRU500A off the top of my head). The DRU500AX supports 4x DVD-+R (yes, both formats), but no mutliformat devices will support DVD-RAM.
If its for movies you want it for (especially as divx -> svcd is very poor) I would recommend the Sony, and try many many different disk brands and types until you find one that works well on your hardware.
In fact, unless you need DVD-RAM, get the Sony. It reatails for around £235 inc taxes (£200+VAT). You can pick up a piece of crud 2x DVD-R for around £130+VAT if you look carefully, but I'd be very surprised if you got a usable movie out of it. Also check the software bundle that you get with it, decent software can be expensive