I guess it really depends on the function of the startup routine. I would say that both are needed, but it's hard to anticipate. A startup event per node might be doing something like flushing out a temp directory, seeding a in-memory database or starting other services. A cluster-wide startup event might be populating or sorting out records in a shared database or starting up shared services. Obviously the second case you only want performed by one of the nodes (or else they are stepping on each other's toes).

-Dan