Quote - (goodcase @ Jul 17 2008, 17:00)

i believe you meant to say "SB 900" and Canon ex 580.
If so, The EX580 would be comparable to the SB800. The SB900 is better than the ex580...so yes. I believe it is better.
Mind you, the SB-800 has a higher guide number than the SB-900.

(and the 580 higher than the SB-800)
The SB-900 is a more creative flash though with a better user interface compared to the 800. (no more d-pad) They finally made the Master/Slave switch physical now.