Projectiles which is more viable network instantiate or RPC

I have been working on a project and have read lots of posts on here about how to do this , and some people prefer to do things there own ways.
I would like to know which is the best and most efficient way to implement a projectile system in my game.
Players can join the game at any time and want everything to be in sync I have spaceships which are network instantiated by the player as these end up being player controlled and they sync perfectly over the network client and server side.