as far as I know xps 17 uses 1 fan set up, both asus and sager use dual fan set up for pulling the air through
as far as dvd drive goes, not really sure, you can call up or email xotic to find out what exact make/model are the dvd-roms perhaps using that you'll find which ones are sturdier.
Here's reviews for sagers:http://forum.notebookreview.com/sager-clevo-reviews-owners-lounges/549118-sager-np8150-clevo-p150hm-review-forerunner.htmlhttp://forum.lowyat.net/topic/1794588
in general I don't think there will be much difference between asus and sager on temperatures if the hardware is the same
as far as dvd goes, I think the difference is that asus has only the tray that comes out for the dvd while the lens and reading assembly is all inside the case, while sager has the whole reading assembly come out of the case on small rails. Maybe that's what you were referring to? 3rd version of cdrom on a laptop is similar to what macs have - just a slit on the side you push the dvd in, it eats it, there's nothing to be opened.