The Carribean is often slight and glassy unless there is a hurriciane around the Atlantic will be more active as its the open ocean away for the most part from land and Islands.
The weather should be genewrally hot but more chance of rain, in Europe we often get USA east coast weather a few days after you, if you have a hurricaine on the east coast the atlantic will be active.
On all of the route its hot the med is very hot indeed during the summer, but for the trip over its late spring and less predictable, rain clouds, and active winds can make a difference, i would say the trip back to the USA is likly to have a higher change of great weather than the trip across in May.
I have been in bad weather in spain in July, in the UK we have had the hottest June on record but then rain came.
Everything is not predictable but I can only say in summary, likley to be more active waves, weather etc on nomal days, ( excluding hurricianes) than the Carribean.