I can see only one advantage to your staying concierge for the one night, but it's a big one in my book. We added a one night stay after our
Disney cruise and I opted not to go with concierge. I think that was a big mistake on my part because our standard room wasn't ready until 3pm. After getting up at 6am to prepare for debarking, it was no fun to have to wait 6 hours for our room to be ready. There are no guarantees with concierge, but I honestly think that it greatly improves your chances of early check in. Worst case, if you do have to wait for your room, you'll have the lounge to relax in.
Tammi