FPS Map Making in Unity? Thread

I'm working on a single player FPS, using Unity, inspired by late 90s FPS games like Half Life and Shogo, but mixing in modern design ideas where appropriate. I'm not too concerned with being technically accurate to the period.

The problem is level design. The more I look into it, the more options I have.

The stock Unity editor is model based, so I considering doing things "Bethesda style" where I'd make some generic peices that snap together.
I've seen people write custom scripts to import .map files (as in, Quake engine maps). Meaning the map can be brush based. It would be a lot of extra work to figure out how to do that, so I'm not sure if it would be worth it in the long run.
I've also heard of people using 3D modeling programs or CAD software to export level geometry as a model and import them into Unity that way. Sketchup comes to mind, and TrenchBrush can apparently export level geometry as a model. Though any others you know of would also be welcome.

There are other ways, and likely stuff I've not come across yet. If you guys have any opinions or advice, I'd appreciate it.

Edited by: SabreXT