asking "which is better: dell inspiron or dell xps?" is like asking "which is better: horse turd or cow turd?".
dells are designed to work great initially, but not keep working that way so that you (a loyal dell [strike]sucker[/strike] customer) go buy a new one. every dell i've worked on seems to have the same problem: somewhere between 1.5 and 3 years they almost suddenly bog down and become half useless.
if you're comfortable building yourself then do that, otherwise find a local computer shop with knowledgable staff (not best buy or staples) and buy a custom built PC from there.