As someone said, get a dual burner. It will do most everything, but beware of cheap media being difficult to burn.
Heck, if you have $100 to blow, go to staples and get the Magic I/O. I have not heard too much bad stuff about it. If you want to spend a bit more for DVD-RAM, then the LG series is good. I think Best Buy had the Lite On for $70 after rebate last week.
Beware of what is advertised as speeds. The Magic I/O above is an 8x Dual Burner. 8x for DVD+R 4X for DVD-R and I forget if DVD+RW is 4X or 2.4X.
DVD-RW might be as high as 4X as well.
In general, DVD + formats have faster burn rates since it was designed AFTER DVD -. I think the DVD + format has not been entirely blessed by the DVD committee. On the lighter side, most cheap DVD players will play all the DVD +/- formats. Older DVD players are more picky. Sort of like the CD-R and CD-RWs not playing in car stereo systems.
Hope that helps.
Cheers.