please help

I am building my purchase of computer at dell.com. I have following questions which I do not know: Thanks for your help in advance

Optional drive:
1.48X CD-RW/ DVD Combo Drive
2.16x DVD+/-RW Drive
Both of the above can wriet DVD? what is the difference? Which one is better?

Modem and wireless:
1.Internal PCI 802.11g Wireless Network Card
2.Data/Fax Modem plus 802.11b/g wireless PCI card

The price for these two modems are the same. which one is better? why


Thanks again for ur kind help