I dont know what was in my head when i posted my first reply, i answered it as if i was thinking of CDR/CDRW...
DVD RAM, -R, -RW, +R, +RW is a new game altogether... And to decide which to go for is almost impossible.
From what i understand, -RW has a max write speed of X1, -R, max of X2.
I think the +R and +RW have slightly less storage capacity.
Now a DVD -RW DISC can only be written to with a DVD -RW drive, as with -R DISCS, and this rule applies to the +R,+RW standard (or lack off). They should be able READ either format however (this i was told).
Apparently because of the lack od standard, SONY has decided to release a DRIVE that will READ/WRITE both DISCS.
The next DVD format (i was told to be called DVD Multi) i've heard will be supported by Microsofts next OS, whether this means it will become the "standard", who nows..