No difference -- personally I'd check around for some opensource file format (or make your own... depends on what features you want it to have... if you just want unsmoothed polygons and possibly UVs and space is not an option then you can use a file like JMS which is uncompiled and uncompressed.

Again -- I need to know what its for to give better suggestions...

Btw -- all a file is is a series of variables... its much more efficient memory, space, and processor (go figure) to use file import then simply bake it in the program. You can load files as much or as little as you wish... a program's inflated if its baked in.