Generally 15.4" is widescreen and usually in WXGA 1200x800 or WSXGA 1680x1050 resolution.
You will find that most of the screens nowadays are widescreen because how humans see, they have a wider field a view then high field of view. This is why it is easier to view a piece of notebook paper in a landscpe format (on its side) rather than straight up and down.
A 15" is usually the old square type screen.
Viewing is personal preference, but for resale down the road, you may want to choose widescreen as not many people want the old square style screens.
Make sure wherever you are looking they are not just rounding the number off (which would be really rare).
you right about that but, can i ask something else is sommething that i have in my mind?
how looks the text in 15.4"monitor,aplications,sufing the net and usually everything else?
is the card card that is intergrated support their resolutions?
as they run in WXGA 1200x800 or WSXGA 1680x1050 resolutions?
thanks once again.