Is 1/2 so much louder and worth upgrading to? and for 2 s4 kits would 3/8 hose be fine for them? I will be running 150-220 psi threw them and dont want to trash them
Yes. 
X2 i have the 1/2 inch
the hose size depends on the tank port or fitting in that port because that’s what’s restricting the air flow, if your fittings are 1/2" then use 1/2" hose, etc…
if you’re driving more than 1 horn from a single hose then that’s different.
it’s a cost thing. a 3/8" hose will usually cost less than a 1/2" hose of the same length.