If points difference was such a 'good' system it'd be used by now in a lot of other things, funnily enough wins is still used in almost every sport with points difference coming as a tie-breaker. All your arguments for the points/round system are literally a reverse of the arguments for the wins system. But the wins system has one major thing over points/round difference. It's a lot harder to win a match than a round, hence why the win is more significant. If you won against team A 5-0 then lost your next two matches either Team A had a rough match or you had one good one before becoming shite yourself and therefore you do not deserve to go through. Because 2 out of 3 wins is harder to achieve than 5 rounds, or one win in a match is harder than multiple rounds to achieve.