AB400 or 800

My studio is 9x15 with a 8' ceiling which light would be best to work with?

I have similar dimensions in my garage which will be turned into a studio soon. I was told that its better to get the B800's because you can always stop down with the light output, you cant add light.

I have a space slightly larger than yours and I chose to get the B800's. I believe that the B400's would do fine as thekid24 says, I'd rather have too much light and have to stop down or use modifiers to control the light rather than being caught without enough light. I also didn't know if I would want to take them outside the studio and opted for the 800's for the same reason mentioned.

Ditto to both posts above. Go with the B800's.

You never know where you might want to use them - even outdoors on occasion. I have done that with mine.

The AB's also have an upgrade policy so you are no locked into a smaller unit. During the first two years you can upgrade to a larger model for $25 + the difference in cost between the models.
Dan

Good point Dan. AB has excellent customer service all the way around. With any purchase you have 60 days to return or exchange for any reason. After than, as you said, for $25 they'll do upgrades. That's a pretty great policy.