@Chris Death
it makes a difference.

ofp can only render ~256 objects at once
even at normal viewdistances.
an other objects wont be displayed.

simply stuff several objects in one p3d and make proper lods
this way you can have much more buildings displayed at once
eg like the ofp forrest blocks are made.

if you only place seperate building objects some far places will look quite deserted.

eg
a.p3d only has 1 object.
b.p3d has 4 building objects.

now multiply with 256

a.p3d will output 256 objects
b.p3d will display 1024 objects.

quite a difference isnt it?