"You can either use the Extended 32 bit version in FS or convert a copy to DXT format for actual flying. The drawback with 32 bit is the filesize (4 or 8 times the size of the equivalent DXT) and performance (DXT formats are optimised DirectX formats and are stored and displayed using the Graphics card built-in DXT hardware). "
Of course, if you have a good graphics card, a GB or so of RAM and a terrabyte of HD space, you could just opt for great rendering instead of performance. That's what 32-bit is for. I've been playing with it recently, and now ALL my DXT3 files (with some exceptions) are 32-bit. It just looks juicier . . .
