Even better and more appropriate comparison.....Arnold as 'Dutch' in Predator/Sly as 'John Rambo' in Rambo
Sly can be very sneaky and sly in the jungle, if you watched First Blood and Rambo he used camoflage very well.
I believe Rambo has Dutch on stealthmaneuvers in jungle-terrain, Rambo seems to be the best in that terrain as well.
Sure, they both used mud, but while Dutch used it to hide from the Predator (since he knew he couldn't see Dutch at all when he was covered in mud), Rambo used it against Spetznaz, which are not dependant on the Predators heat-vision.
I also believe Dutch would make a bit more sound in the jungle and be a bit clumsier, since he is not as agile as Rambo in that terrain.
It all comes down to who would step on eachothers boobytrap first, since they would not fight eachother in the open (if the battle was taking place in the jungle).
If the battle was taking place in a small town like in First Blood, anything can happen, since they both would be armed with heavy machineguns etc and Rambos agility would be less of an advantage there.
In the Jungle : Rambo
In a small town : Even
In a close secluded space (Red Heats Sauna) : Dutch
