02-18-12: EldartfordNo question about it. As we discussed in this thread, in a properly gain matched passive biamp (or triamp) arrangement there is no division of voltages between the different amplifiers, just a division of current and power. If there were a division of voltages, it would mean that gains are not properly matched, and frequency response flatness would be thrown off.
I have found that with a real music signal the peak voltage swing requirement for the higher frequency signal is only met by a power amp with substantially greater power rating than that based on equal power.
(In saying that, I'm neglecting small voltage differences that may occur under properly gain matched conditions if a tube amp having significant output impedance is involved, AND if the speaker presents significantly differing impedances in the frequency ranges handled by the different amplifiers).
Concerning the OP's question, I would expect that which configuration would provide better overall results will depend on the specific amplifiers that are involved. But fwiw my instinct is that it is generally best to go with a less complex solution (Option A in this case) than a more complex solution (Option B in this case), unless there is a clear reason to do otherwise. Or unless there is an opportunity to try both approaches, and compare.
Regards,
-- Al