Different broadcast but not louder or quieter. In a 2x12 there is some signal pushing/spreading/overlapping/cancelling shit going on in the middle zone. spreading 2 apart or at different angle's would eliminate that happening despite the fact nobody really hears it happening but in reality it's that jai ne sai qua that make multi-speaker cabs sound bigger.
I did the 2 of 1x12 for a bit, like it just fine, used one as my monitor alot or angled one towards me, other middle of house. Eventually, gave up on it. More hassle than worth at the time.