Before revision:  With conserved total particle number, dispersal has no effect on survival probability , while with birth-death fluctuations present, moving slower is the optimal strategy for the weaker species : it is imperative to include fluctuations to properly formulate survival strategies.
After revision:  With conserved total particle number, dispersal has no effect on survival probability . With a fluctuating number, faster dispersal is advantageous if intra-species competition is present, while moving slower is the optimal strategy for the weaker species : it is imperative to include fluctuations to properly formulate survival strategies.