Knowing which DVD drive you have really helps when deciding which media to buy and why it will or won't work. Each drive has its own strengths/weaknesses so knowing which one you have really helps. You don't even need to open your xbox as each brand has a different disk tray! hooray!
Samsungs are usually deemed the best drive to have, they *usually* can read cd-rs, cd-rws, dvd-rs, dvd-rw but no dvd+. Thompson are occasionally deemed the worst xbox dvd drive, they rarely read -rs but can read dvd+s. They are also known for their laser wearing out quickly. HOWEVER - every drive can be different. THERE ARE NO STEADFAST RULES. So before buying 1000 DVDs, check they are compatible with your dvd drive.