The PD 186 will have the higher output in a horn loaded cab. If you look
at the specs for both drivers you will see that the 184 has the higher
EBP so would be better suited for horn use. The 186 has a higher Vd so
will always be able to move more air at lower frequencies than the 184,
but for a given input the 184 will have about 2-3 dB extra output. So it
all depends what you want. If you are never going to drive hell out of
the cabs and aren't after maximum SPL then the 184 would be a better bet,
it will give you more output for a given input level, it will also give
you a quicker transient response. If you most have that extra 1 - 2 dB
of extra SPL and don't mine having to drive the cab with huge amounts of
power to get it then the 186 or ideally the 1850 are the way to go.
After doing listening tests you will find that both drivers are quite
close in performance. You will find that the 186 has a very smooth Hi Fi
kind of sound, but is a bit slow sounding. The 1850 has a very hard and
grunty sound in comparison and the 184 sits somewhere in between. The PD
186 driver is best suited to reflex or bandpass enclosures.