400 Watt MH or 150 Watt HPS??

I currently own a 400 Watt Metal Halide lamp and ballast, as well as a 150 Watt High Pressure Sodium lamp and ballast. I decided to grow my first autoflowering strain. Since I can't use both, my question is which would be best?

400w mh with about 200-300w of 2700k cfl

Straight choice?
The metal halide.
If your willing to swap out lights mid grow might be worth considering vegging with the MH, flowering with the HPS and getting some cfl's to go with the HPS.
Kinda hard to say without more info (grow size, plant number etc. etc.)

Thanks for all the help. I was only growing one Trans Siberian Auto, hydroponically in a 3x8 closet however I added another hydro setup containing 5 photo type plants. Because of this I caved in and ran them both with the HPS primarily on the auto and also added two T12's.

Why cant you use both lights?

I wasn't considering it due to poor ventilation but I did some reconstruction (~} and installed some extra vents and fans.