I think you need more specifications. How is each person built? How does everyone on either side collaborate with each other? Are there any weapons involved, or is it purely a battle of strength? How is everyone positioned? I'd probably say women here without extra context, assuming everyone is of average strength and it's not a fight with weapons, purely because there are a LOT more of them and they could easily take down the men. If it were 500 women vs 500 men, again without a lot of context and just assuming, I'd likely say the men in that case because the overall average strength for males tends to be higher than that of the average strength for females.