The advantage of connecting in AMS (or CDG) is that if there is a misconnect, there probably will be another flight in a couple of hours. If you misconnect at JFK then it is the either the next day or another connection at CDG/AMS.
If it is "meet up with a group" as in a group tour where you are canceled if a no show, then I would go the day before. If the group is a bunch of friends headed off somewhere that you could meet up with later in the day, that is another thing...