Don't think "most kills wins" will make people play more aggressive. They might play more aggressive if the round is already lost to try and get a kill or two. But the majority of the round will just be the same. And the result will still be the same, as whoever gets the most kills also wins the round. Thus the same team would most likely win and it would NOT make for a more aggressive playstyle. It might even make people play a lot more safe, as dying means the enemy team gets a point.