7. IRV encourages sincere voting rather than disingenuous tactical voting
To accurately aggregate individual opinions into a community decision, a voting system should encourage citizens to honestly vote according to their consciences. With our existing system, some voters struggle with the decision of whether to vote for the candidate they actually prefer, or whether to vote for a perceived "lesser" candidate who may have a better chance of winning for fear of inadvertently helping the candidate the voters like the least.
Various preference voting systems other than IRV, such as approval voting, Bucklin voting, and at-large multi-seat voting (actually a multi-vote no-preference system) suffer a similar problem of insincere tactical voting. Voters who honestly express their second or subsequent choices on their ballots may be penalized since those alternate-choice votes may cause the defeat of their most preferred candidates. The "smart" voter with a strong first preference will "bullet vote," refraining from expressing any alternate choices. This is not a difficulty with systems such as IRV, however, since voters who select second or subsequent choices will not thereby help defeat their first choice.