Both are grammatically correct. I prefer "Get off of the bus""

logically: (get off) [of] {the bus} = get (off the bus) but note: get on the bus = correct get on (of/from/to) the bus = wrong

Both mean the same thing and are grammatically correct but [get off of the bus] sounds better

You could say either but "get off the bus" is much more common.

The standard English form is 'get off'. You get on a bus and you get off a bus. 'Get off of' is a regional variant. It is only used by American English speakers.