Venom, whether or not you remap is up to you, and in large part is based upon how your textures look
in game versus how you
want them to look.
I can see why you
think there isn't a difference. However if you make a backup copy of the texture map shown in your screen shots and write that Arial 10 point text across it like I suggested and rerun your test you
will readily see the difference

If you look
closely at the two screen shots you posted, you
can see the textures are being reduced. The most apparent area you can look at is where the front of the "engine cowling" joins into the "midsection" of the body, there are some distinct horizontal lines in the ModelView shot (dark grey) that are missing in the ingame shot. You can also look at the striping on the gun barrels and see the blurring induced by the reduction. There are other areas it can be seen in, those are just the easiest to see.
However for your model and your texture maps, the end result isn't that large of a difference. The big key is how fine of detail there is in the original texture map and how much the reduction is. Going from 512 to 256 isn't near as bad as 1024 to 256 and mottled patterns being reduced aren't near as apparent as surface details created with fine lines that have been reduced.
Aldo... I don't use lithunwrap for two reasons. First it requires triangulated polys and second it doesn't have the versatility of uvmapper in regards to selection of polys based on material, group, or region. If you use uvmapper, then you could more easily create the top/bottom/sides/front maps you are thinking of doing by first generating a cubic mapping with seperation between planar views, then assign the various views to seperate materials, then expanding the material regions to the full size of the map and saving the individual views as seperate maps. The down side is it only works with OBJ files in wavefront format so you have to go through some conversion.