MTF: Demon Hunter 3: Which way to go?

Currently in the writing of the story, the Demon Hunters have found their target. I'm at a crossroads of how to write it up.

Do they see the enemy so they have a clue what they are facing? Visual references would include how SG-1/Atlantis did things, Starship Troopers seeing the bugs for the 1st time, etc

Or do I keep the creatures a secret so when they run into them, there's a better chance of the reaction from the team? Doom, Alien(s), Predator, etc

Decisions, decisions. 

I'll probably do 2 versions and see how it flows.

Demon Hunters - Lt Rocker