I went by both means of transport: by ferry (10 years ago) and by bus (6 years ago). So my experiences are a bit outdated. Both visages were from Split to Dubrovnik.
I had luggage both times, a suit case and a travel bag.
Boarding the ferry meant climbing rather narrow steps up to the passenger deck. Proper sitting was only available in the restaurant where we went for breakfast. The remaining hours we managed to sit on a casket where life vests were stored. On arrival we could want to a bus stop and wait there. No taxi in sight. Today with Uber this might be a different situation.
Going by bus reassembled of a time travel back into the old Yugo times: the driver asked for extra additive tax per person (we went with locals and they were likewise surprised). We witnessed smuggling at the boarder by the driver and co-driver and when in that small Bosnian corridor they went off for a 30’ or so break. - In these terms I think the new bridge is a blessing, making the bus journey a more comfortable affair.
I personally would opt for the bus.