It depends how good the performance is. Our event in Namibia was just brilliant. It was onboard, but the three acts we had were amazing. Personally we preferred it to the last few we’ve been to onshore where we had to queue up to get on a bus, go to a large tent at a hotel, have a drink and a snack then sit & watch a performance, then queue to get back on a bus, effectively taking up a whole evening for a 45 minute performance.
If it’s off the ship then it needs to be something really special to justify the queuing & standing around, not just a performance that could be done in the cabaret lounge on the ship.