The one worth watching.
Yes, this is the one with Arnie, and the better of the two, in my opinion.
So off Arnie goes to get the holiday memories, he is asked what he wants to be, and picks a secret agent that will save the planet. During his implant procedure something goes wrong, or does it?
Apparently he is already a secret agent and has had his memory wiped, so now he is solving the mystery of who is actually is. His investigation lead him strangely enough to Mars. There he discovers that the administration running Mars is corrupt and that he was a part of it.
But he is a good man, and can't let things go on, so he must bring down the system and free the people on Mars. Strange how this is also along the lines of what he wanted to be implanted. This angle is quite reinforced enough in the movie. Hence, this is much more of an action movie for Arnie, than what could have been a thought provoking film. Either way very much worth watching.