The question over which format has the most players is unimportant. By the time DVD rewriters replace CD rewriters as the norm (perhaps next year), these newer, faster, and very much cheaper drives will all support both standards.
There is no particular reason why DVD rewriters should not drop to near the price of CD rewriters. By the time one of the two formats wins, those few stuck with the wrong single standard drive will be able to upgrade for a small fraction of the cost of their original drive.
Given dual standard drives, this will be not so much a DVD drive war as a writeable DVD disk war. There is no particular reason why it should be more difficult to produce one disk rather than the other, nor any great difficult in changing production from one to the other. The relative quantities of disks produced in each format should follow demand.
Spath gives good arguments for the DVD+R(W) disk being superior at high speeds. The new Plextor dual format drive (Px-708A/UF) writes DVD+R at 8X, but DVD-R at only 4X. That is some proof that his arguments are correct in practice. It would, admittedly be better proof if 8X disks existed.
The only reasons I can imagine for DVD+ not being the ultimate winner would be excessive royalties demanded on the blank disks, or some sort of legal battle.