They are both transported into a battlefield, pretty open with hills of wreckage and skulls and shit, like in Terminator and are told to kill each other for the glory of the Emperor.
Info on the Dark Trooper:
The Dark trooper has limited use of the dark side, it has an advanced sensor system and it can also fly.
Their exo-skeletal armor provides them with enormous physical strenght also.
Their armament includes heavy blasters, wich is most likely in the tens of MJ range and they have missile launchers and they can fire some kind of weapon from their chest, it might be some kind of flamer, firing balls of napalm-like material or something.
Here's a Dark Trooper(I've been told it's a Mk. II, but from game screenshots it looks like a Mk. III):
And here we can see the sizes of the Dark Troopers relative to a C3 Droid:
Info on the Space Marine:
"The Space Marines - Created in the distant past through genetic manipulation and arcane science, Space Marines are Humanity's ultimate warriors, dedicated to the defense of the Emperor and the Imperium of Man. A Space Marine army is a compact force of elite warriors each one the equivalent of ten normal men. From the steadfast reliability of a Space Marine Tactical Squad to the alien-blasting power of the Predator Annihilator Tank, a Space Marine Army is flexible enough to defeat any opponent."
They got Bolters and Powerswords and plasma guns, it depends really, I dunno what a vanilla Space Marine would have.
Space marines are pretty big, 8feet tall IIRC.
This one is linked, rather large(and a really old one too, 1st edition I am told):
http://hisshadow.123hostnow.com/misc/im ... mer40k.jpg
OK, so now you ought to have some basic info on both of these guys, well, the info on the space marines weapons is lacking really, I didn't find much info on him, hopefully someone will complete that gap.
