ok i work in a kind of tangential industry and can kind of answer this probably

in general the higher the voltage the smaller the current, which you're generally happy about because your 1) electrical losses and 2) cable/wire diameter are both proportional to current

the tradeoffs being 1) it gets harder and more important to isolate the circuit (e.g. your wire insulation that prevents the 12V bus from shorting out to the vehicle chassis now needs to be thicker) and 2) all the stuff people make for cars (i dunno, windshield wiper motors, radiator fans, whatever) is currently for 12V

in general this move probably makes sense, provided they're able to figure out their supply chains, and if tesla can position themselves as being like the first company to figure out a bunch of these 48V components at scale that's probably going to be really good for them. they did a kind of similar thing with the charging infrastructure if i understand currently, like now the tesla charging cable is the de facto north american standard