Which one do you like?
Dell Inspiron I580-5108NBC with Intel® Core™ i5-650 processor
Features a 4MB cache and 3.2GHz processor speed. 8GB DDR3 SDRAM,1TB Serial ATA hard drive (7200 rpm),NVIDIA GeForce GT220 graphics
for $800
or
Gateway DX 4831-01e with Intel® Core™ i3-530 processor; 6GB DDR3 memory; DL DVD±RW/CD-RW drive; 1TB hard drive; for $560.

For "me" I like the i5 for they are a higher-end line of processors. But the i3 line will serve most normal users just fine. Since you did not say what you plan on doing with this computer, NO ONE here can advise you which is better for "you".

They are both reliable.

I recommend the most expensive one nah but seriously:

Dell Inspiron I580-5108NBC with Intel® Core™ i5-650 processor
This one would be better for gaming

Gateway DX 4831-01e with Intel® Core™ i3-530 processor
Is better for everyday use.

But yea I agree with the guy duck avenger avatar