It really depends on how many folks you plan to have on board to help with your passage. I can report that our 47 footer is more than enough boat for us as a couple and has plenty of room for two more couples to comfortably join us.
Another thing to consider is general cost of
ownership differences. The 50 will cost more to
haul out, and maintain. The 50 will cost more each time you decide to pull into a marina. Depending upon where you sail in the world, air
draft may become an issue. As an example, around the
gulf coast most bridges are reported to be 73 feet. The
mast head on our 47 is just under 71 feet. I spend a good amount of time looking at tide
charts and pulling water level measurements from monitoring stations just to make sure we can get under with only minor
antenna dragging. My point being is that it results in anxious moments each and every time. The 50 footer will no doubt have a taller rig and may limit where you can go.......again, depends upon where you will be using the boat. The extra 5 feet will give you more space, but I doubt that it will make that much difference in handling performance and ride.