In my opinion, the first kill is better than last kill, because this way snipers, or defensive playstyles in general, have a chance. How many times has it been that a defenes playstyle was topped by just one good charge? If a line of defense is broken it is so much harder to come back than coming back after a failed charge. Whenever I played against a team that tried to hold the line instead of charging us, we won the second we broke through.
Snipers can't run, can't chase, just stand stll and shoot when they actually see something. A brawler team can almost always escape snipers, even on Dunes. So if the brawlers get the first kill and hide, the snipers have enough time to move out of their defensive playstyle, since they know from the very beginning that they are at a disadvantage. If they don't then it is going to be a boring match with nothing happening and the snipers lose, too bad. In reverse, the snipers get the first kill, well, only one good charge is needed for the game to be over.
In matches that are sniper vs sniper or brawler vs brawler I would agree that the last kill option might be better, mostly for the audience, since teams can play a bit more daring and not face an immediate disadvantage. However, teams didn't play more daring when this rule didn't exist either, so for some nothing will change.
A referee also has an easier time tracking the first kill than the last one, because the first kill happens only once, while every other kill could be the last one.
I also disagree with the extra time thing. In counter strike they don't add more time, because the guy defusing the bomb needs that much more time to win. In games like Tribes:Ascend, a capture the flag oriented game, and I am not sure if the following goes for tribes comp too, you get overtime, during the draw until the flag is captured or when a team is one score behind and currently has the chance to make it a draw so they can play for longer with overtime. It is like that, because the flag can be on the run numerous times without being captured. The bomb has a limited amount of times where it can be planted and defused.
In smash bros the game ends when the time is over, even if somebody is guaranteed to get ko-ed.
Smash bros is similar to GOIO in this aspect. When you are too slow to get a kill, than be faster next time. Figure out where you failed and the enemy succeeded and build on that.
