nope not my question... my question is basically "is wattage only factor in spl output" -tard ***
To answer your question several controls must be in place:
first same vehicle, same sub, same box, same everything (even the humidity) except for the amp.
now take two amps, maybe a jl 1000/1 and another amp with rated 1200 rms
now bench those amps under the same conditions and lets say that jl puts out 1200 rms at 1 ohm and the other amp 1400 at 1 ohm at 14.4v.
now lets say that the bass boosts and all other "sound tuning" is off and the only difference between the two trials is the difference in amp output (clean, undistorted power).
If the sub can mechanically handle both amps, the amp with 1400 rms will be louder than the jl.
as everyone have already said, a watt is a watt, just as ferrari 50 hp is the same as a kia 50 hp.