There is no difference in power output between 4 ohms bridged and 2 ohms stereo. Except that in 2 ohms stereo the damping factor is higher(Vikings theory haha)
Good question abe.... It is of my opinion that there is no pro's to wirening an amp in mono. When referencing to an subwoofer situation... An amp that is , say 2 ohm stable, will put out no more power in mono at 2 ohms than at stereo at 2 ohms per channel. The only REAL benefit of wiring up a speaker in mono on an amp is the fact that the signal itself becomes mono, no stereo information. Which is fine in a non-directional speaker such as a sub.
That and it is impossible for minor differences in left and right channel input level to have an effect in a common chamber multi sub enclosure.