I would rather leave from Miami than NY. Traffic, parking and hotel costs. Just using a smaller city as the port.
October is the wettest month in Bermuda. Air temps are still warm, but you gave to decide if an average water temp of 79 is too cool for you. We did not get in the water during an early September vacation. You are sitting out in the Atlantic at the same latitude of approximately South Carolina.
Both destinations have the risk of hurricanes at that point.
As far as ships, I am a Magic over Dream fan. You just have to decide that for yourself.
I assume you get to stay overnight in Bermuda? Not something you get on most cruises - you might consider it a plus. And it gives you an opportunity to dine at Tom Moore’s Tavern for dinner. We really enjoyed our evening there.
And how would you feel about no visit to Castaway Cay.
(I pretty much see this decision as a 50/50 split in my mind. It comes down to intangibles or cost and transportation issues). Having done a bunch of cruises, but never Bermuda, I probably would try it if the price of everything was decent.
Are you leaning more towards one?