Linear or Open ended Thread

I am a making a first person shooter level for my game set on a space station. The mission/objective for this level is to find a scientist who is in trouble on the space station and get information about the enemy you are supposed to kill. I am not quite sure what I want. I wanted a tribute to the original Half-Life and I wanted it to be open ended and have all these things I wanted in that game that I never got. I kind of want it out of the door. I am getting bored of writing a script and I want to finish it. So what do you think it should be? Pick your/my poison.

Open level design with backtracking, pacing.
-or-
Linear level fast paced killing and action yet with lots of jumping and puzzles.

P.S.
I am also having trouble developing the atmosphere.

3DWorlds wrote: I am not quite sure what I want. (...) I kind of want it out of the door. I am getting bored of writing a script and I want to finish it.

If you don't know what you want, how are you supposed to implement it?
Write a script, even if it takes some time. Define what kind of experience you want to create. Make drafts, prototypes and implement small sections to see if they work. Then iterate on your design and add refinements as you go along.

I can imagine that you 'feel' what kind of game you want to make. But that is actually not enough when making games. You have to think rationally about a lot of stuff that players usually take for granted.
Also, write down your ideas. Do it immediately instead of waiting for the next morning, otherwise you'll forget them. Trust me, it's better to do it right away.
That's all the advice I can offer you for now. Hope it helps you a little further.