I guess this is a moot point but, I have SGM and it looks dark on a cloudy day and looks light grey in the bright sunlight. I did see a space grey on my dealers lot on a 3 series and I liked it, but not as much as SGM.
If I was buying an '09 135i it would be between space grey and silver. FWIW
Here's a pic on a sunny day after a fresh wax. And one at sunset.
I love this car..