Space just does damage when they enter non-combat commands. Such as get 1. or scan e.

You might be thinking of Landside of the Second Breath? This gives a driving lag.

In terms of Space vs. Flow I look at them as an aggressive build vs. conservative. Space will likely net you more kills, but Flow will save your ass where Space won't.

If you think you're skilled, I'd go Space. If you're new to the build I'd take Flow.