1pc 2gb ram vs 2 pc 1gb ram

[Den807]

i was thinking of getting the corsair 2gb (dual) ddr2-800 pc2-6400 Corsair XMS2 (Twin2X2048-6400)

is this a 1 pc 2gb ram or a 2 pc 1gb ram

and if it is a 1 piece, is it better or a 2 pc is better?

lastly i only have 2 open port for my mobo so which would be better?

 

[mindless728]

why not get a 4GB (2x2GB) set

 

[Den807]

hmmm budget constraints and the mobo i have could only support up to 4gb ram,