Well you should consider one great advantage of a Dual drive, you can use the media that is cheapest for the moment (or rather the less overpriced media).
Most people agree that + will win the battle, but it will take time before we have one standard.
About the speed: 1x on DVD is a looooong time, remember that

Sony and NEC's dual writers are the most popular at the moment, with NEC having the more attractive price (from what I've heard).