The binary in the title is an exaggeration to make a point, it's not meant to be taken literally. It is directed toward those who think they want monogamy (usually because it's more socially acceptable than poly) but then break up with someone the second the relationship becomes less than passionate (which isn't what monogamy is other than some very specific edge cases)

As to my thoughts, I don't think either choice is universally better than the other. Both are valid, both have drawbacks and advantages and you just have to figure out which one works for you and be honest about it with the people you date.