The only boat I would feel safe aboard crossing an ocean would be an ocean liner. If I "theoretically" had to cross an ocean on a pleasure craft it would be on the biggest, most well equipped, self righting sailboat that was purpose built for that voyage. Maybe an Oyster or a Swan?
I was once on a cruise ship heading from California to Hawaii. I was standing on our terrace watching a beautiful sunset when the ship passed a sailboat which was some distance off our port side. It was under full sail. My guess is it was between 50 and 60 feet in length. Problem for me was that despite its size, it looked like a toothpick floating in an endless sea. That ended any desire I might have had to be an adventurer.