Dvi cable or vga cable?? My new samsung tft and 9800gt card have both vga and dvi ports?

I want to know if i should connect my new tft using dvi to dvi cable or a vga cable as my tft and pc has both ports. The shopkeeper says dvi has much better quality of pictureover vga cable?? Is it true or is the shopkeeper trying to sell me that 700 Rs cable??