The difference is that Poland played awful football, while Argentina showed their true skills. I really regret Mexico did not qualify, as they showed much better show. On the other hand what we have after years are just a numbers and results. Both Mexico and Saudi Arabia had chances to leave the group, for Mexico it was just more difficult. But honestly speaking the cascade of rules (game result, goals, number yellow cards etc) makes all sooooo complicated.
Mexico had a lot of desires, it's just that Saudi Arabia is now playing better football than it was a few years ago. Yes, all the teams in this group had chances, and perhaps Poland did not play the best way, but they are in the playoffs and this is a good result. Perhaps France was lucky that it was Poland who became their rivals, because France is very unstable and Mexico would have a better chance of defeating them.