My first DJ frame was a 09 Komodo. I'm just about that same size as you and would recommend the medium. I still have the frame if your interested LOL!
Kinda funny, I just bought a Spank Spoon frame a few months ago. Had to get it from the UK. I LOVE it!
Are you riding in the street urban style or in the dirt? The Spank Spoon is a designed specifically for street / urban DJ use, which is exactly why I bought it.
If your going to run a single speed, I would spend the extra money and get for a frame with horizontal dropouts, so you don't have to mess with a chain tensioner.
As for Steel vs Aluminum, I personally like the steel. It really is up to you though.
Once I finished building it: