I’m not very well-versed on all this but it seems
First Past The Post
Benefits the two parties in a two-party duopoly system like that of the US. Boom or bust, black or white. When the party in power pisses you off you vote their competitor even if holding your nose.
Seems like there must be a better way, maybe just not as good for those who prefer shooting fish in a barrel
You end up with the actual preference of the majority best represented. You don’t get put in a spot where you have to choose one of Trump or Clinton based on which extreme is least objectionable. You can vote for someone sane, then choose between the two extremes as your “worst case”.
It allows moderates to actually be represented instead of primaried out of the race, then scared to be in the general election because they might spoil the race for their party’s winner.
I explain my rationale in a response to the guy that I responded to. I realize it’s a thin distinction, but I think it’s an important one.