DVD Combo or DVD ROM?

I am a film freak!! My question is that is it advisable to buy a DVD Combo drive to regularly back up movies on a hard drive ( i already got a GSA-H20N)? Or is it much better to buy a DVDROm?
And plz. plz. advise, which brand is better for which writer/ROM (eg. LITEON, ASUS, SAMSUNG etc.)