Kills count. Room creator decides on up to 7 rounds, the Arena itself is smaller and shrinks faster. On the other hand, there’s no Dianoga, so, take comfort in that. Every round ends when there’s a last Snook in the Arena. However, as hinted above, in this Mode winning and ranking is based on number of kills. Every kill grant the player with +1 points and every kill-by-wall (suicide) penalty the player with -1 point.
So, if a Snooker is not aggressive and uses the famous Monty Python “run away” strategy, he might survive till the end, but he will receive no laurels. Just mockery. In case of a draw the winners split the allocated prize.