Which is better lateral or vertical bi-amping?

Once again it swirls around my head-if I have a an amp with a mono conversion switch,power and headroom aside, am I better off feeding one amp to the hi-frequency and low frequency drivers or running the amps vertically.I know that when you lateraly bi-amp you get 150% of the power of the two amps i.e. two 100 watts would mean a delivery of 150 watts whereas many amps that convert to mono will double in power.But I am under the impression that sonicaly lateral is better as you simply get better results where the amp is dedicated to a narower set of frequencies.True?
I have heard that vertically (each amp feeds the low and high of one channel) makes more sense, since there will be more headroom than if one amp handles just the low frequencies. On a deep bass note, in a horizontal arrangement, the bass amp will be driven hard, where the mid/tweater amp will be "loafing". Of course, many people will use a S.S./tube bi-amp configuration. Naturally, a horzontal arrangement (tubes on the tweaters) is used!
Listen to your system both ways and see which sounds the best. I'm assuming both amps are identical from your comments.
It seems that a lateral configuration would minimize any character differences in your amps from the right to left channel. This should not be a problem with high quality same model amps but something to consider.
Chazzbo and Griswold, offer the best arguments while Fatparrot's suggestion would certainly be worthy of consideration with lesser amps. Ideally 4 mono amps carefully calibrated would be ideal for bi-amping. Due to a less extreme frequency demand there would be less electronic gymnastics and inertia from impedance loads ,etc., running laterally. With better dual mono stereo amps one channel couldn't pick up the slack of the less demanding frequency requirements. Of course the all mono or to a lesser extent dual mono amps offer better seperation and consequently less cross-talk.
My assumption is that two lateral stereo amps from the same model would be close enough in calibration than not.Crosstalk well that would end up being a problem if I were to just use the amps stereo fashion vertically.Problem is not enough amps even in the high end offer mono conversion.I was thinking of finding another PS Audio Delta 100.I also have have a Mesa Baron but doubt I'd need 225 watts (again with a horizontal arrangement w/150 watts full Pentode))or even 135 wpc if a second were obtained and both run in triode (as they 90 Pent-of course this can vary with the Baron as you can set Triode and Pentode in thirds).But this would come into play if I got a Kora Cosmos 50 watt and wanted to add another.This arrangement to me makes a lot of sense for those who want more power from an intergrated amp.I had thought of going this route with a high cost to performance company like VTL or Rogue.Makes me wonder why a company like Cary ( a freind I know really enjoys his)has a fine Intergated amp but does not offer a companion piece.Or if a company does why they might not spend extra to add a mono conversion.
Chazzbo, you might want to look at the Cary web site. They have an interesting point of view re: bi-amping with thier Rocket intergrated. I am neither in favor or against their point of view.