Does the number of BTUs required to cool a room vary between cooling methods?

For instance, should a central HVAC system provide more or less BTUs than a window or wall unit?

The reason I ask is that a HVAC vendor is claiming the BTUs required to cool a room is twice that of wall unit manufacturers.

it takes 12,000 btu`s to make what we call a ton,18,000btu`s = 1.5 tons. It is the same wheather it is a window unit,, through the wall unit, or a split system / central ac unit. A central unit is much more efficient because they can distribute the same amount of btu`s into more rooms or area,when you are using a window or through the wall unit they normaly are used to cool only one room or not much more than that. To cool a second room or area you would probably have to make the room where unit is located much cooler than some would like it so as the cool air would get into the second room or area. So in other words if the air is ducted to other rooms through a central system you can get more use out of a smaller BTU system,, not for sure if this will help to answer your question or not