The recommended Common Good voting system is a combination of many democratic methods, each of which has its own virtues (see "Where Is It Used") and shortcomings (see below). Here are some of those components and their shortcomings, in comparison to the recommended system:
Simple majority vote (first-past-the-pole plurality) gives voters no opportunity to voice their second choice. As a result, in multiple option votes, people tend to vote for an option that they think might win, rather than their top choice. Majority vote gives no voice to the minority and fails most voting criteria.
Approval voting, without ranked pairs, gives voters no opportunity to express a preference of one choice over another, unless one of those choices is completely unacceptable.
Condorcet voting, without vetoes, gives no voice to the minority's strongly held beliefs.
Consensus decision-making is often unworkable in a large group lacking any ideological common bond and having occasional sociopaths. The Common Good Democracy operates in a spirit of consensus without getting waylaid by difficult individuals. A variety of deliberative methods and consent-based decision systems, such as sociocracy may be used before framing questions for a vote.
Hierarchical decision-making (for example, the president decides everything) disempowers and alienates people from the community. The recommended system empowers people and brings people together.
Representative democracy, without optional direct voting, dumbs us down by choosing one person to think and make decisions for a multitude, despite the desire and ability of many constituents to participate in such decisions. (Many heads are better than one.) When elected by majority vote, the representative cannot plausibly represent the constituents who voted for someone else.
Direct democracy, without optional representatives, leaves out everyone who doesn't vote directly.
In-person voting (such as in New England town meetings), without optional voting from afar, leaves out everyone who doesn't come to vote in person.
Internet-only discussion and voting misses out on the community-building experience of in-person discussions and visits to the voting site.
Budgeting by yes/no votes on line items proposed by committee, leaves very little choice to the voters.