The problem with non-compulsory voting is it means that only the people who care strongly enough about the elections to get off the internet and drive to a polling booth are the ones who have their voices heard. This means that you lose a lot of moderate, sane, rational voters but keep all of the rabid nutjobs.

OTOH, you lose a lot of ignorant, clueless, or just lazy voters who have no basis for forming an opinion, and the ones who have the voices heard are the ones who cared enough to study the issues, even if their study was one-sided.

Push the problem a step back, and my thought here is compulsory political study rather than compulsory voting.