Your question is only easily answered if the cabs have the same drivers, ohm rating, and frequency response.
In theory:
Double power- add 3dB
Double cone area- add 3dB
Halve impedance- add 3dB (but only if amp can give double the power.
Ten times power- add 10dB.
Note: 3dB is typically enough for the untrained ear 'to hear a difference'. 10dB is 'twice as loud' (at mid range frequencies and average volumes).
Bass needs about 10dB more to sound louder than just an octave higher (guitar) due to psycho-acoustic effects (loudness curve), which is one reason why bass amps need to be so powerful.
The EASIEST way to sound louder is to get a more efficient drivers in a well designed cab, which is why some of the small, light modern cabs sound as loud as old fridge-sized 8x10 cabs.