There is no point in spending twice as much for a dual format drive.
Let's say you can buy a $150 single format drive, or a $300 dual format drive. If I buy the single format drive, worst thing that happens is that in 1-2 years, I won't be able to find media to burn on my drive. At that point, I'm going to have to buy a drive for the opposing format. Funny thing about computer parts, but evidenty they get faster and cheapter over time. Or so I hear.
So, in those 1-2 years when the opposing format wins, I'll probably be able to get another drive for $50-100. Let's say it's a $100. Total I'll have spent is $250, which still puts me $50 ahead of buying the dual format drive. And, my new drive will probably be 8x, 12x, or maybe even 16x. So I've spent less and I have a faster, newer technology.
Now, here's the kicker. Let's say that my format of choice is the winner (or, more likely, there is no winner and you can buy media for both formats.) Then, I've saved $150 and I can still burn DVD discs.
I think the dual format drives are highly overrated on this board.