Short: better use “/” just when you need to change actual path or call functions not directly on root.
Just some examples:
http://forum.mikrotik.com/t/rextended-fragments-of-snippets/151033/1
About spaces or /
Since 7.x it’s all than really done, and for other reasons,
better use space for thing shared with v6.
On things like wiregard etc. that are available only v7, not mind but better use “/” instead of space.
For me that I write script running on both, I prefer the space.