There are loads of discussion threads that "debate" the concept. What Bolero said is part of the equation. The difference in cabinet size will alter the frequency response of the system, which might affect how you perceive the sound.
Mathematically, if you put 1 watt into a 100dB efficient speaker, you get 100dB. If you put 1 watt into 4 100dB speakers wired to the same impedance, each speaker will get 0.25 watts. Thus each speaker will be putting out 94dB (3dB for halving the power, 3dB for halving THAT power.) But then you had 4 times that 94dB and you get back to 100dB. The difference will be more in tonal balance that actual sound intensity, which might be measured at 1 frequency.
I've seen discussions where they say the increase was larger with 2 speakers rather than one, but the problem with this is that the impedance won't be the same between a single and a dual speaker setup. If you have a pair of 8 ohm speakers, and only use one, it's 8 ohms. If you add the second in parallel, it's now 4 ohms, so your power usage is different at the "same setting". Put them in series and you have 16 ohms, which could lower your output.
When you use a 4x cabinet, with two in series and the series in parallel, the impedance can be the same as a single speaker. Identical power is distributed evenly.
Jim Lill did a Youtube video where he compared lots of difference cab configurations and how it affected the sound. It may not change the dB reading but it changes the perception of the sound.