I usally go 4 to 8, depends on the track tho. thats what i do by default but if the dude thats gonna rap on it wants a longer or shorter chorus ill change it up to whatever they want.
as a general pointer you want to flip the drums, melody, or both in the 4 to 8 bars before the chorus and then break into a consistent 4 bar chorus looped to 8 bars. try to keep the chorus simple because it should be the anchor of the song between your 16 'verse' bars that should have some drum flips and sample flips built in.
ok yeah.. I been listening to a lot of songs and it doesnt even sound like the producer changes the beat.. its just a lopp no verse.. chorus...verse set up.
^^^^Depends on the beat... half the songs have the same beat going throughout the song with no change ups in the choruse, and half do... but it's more interesting if there is a difference....
sometimes, especially if its a sample. theres just a 4 bar loop wit some breakdowns, but other layerd instruments/samples are accepted as changeups. hope that made sense