If you're only priority is to extinguish the flame then go ahead and use BC. If you happen to catch the fire early enough and you'd like to make any salvage attempt a bit easier I'd go ahead and spend the extra money on a Halon/Halotron fire extinguisher instead. The difference is whether you want to pay for it now or pay for it later.
Anyone priced two and a half pounds of Halon recently? Somewhere in the $150-200 range. I'll stick with the $35 2.5lb BC extinguisher and deal with the cleanup. If I'm spraying it it probably needs to be replaced anyway.