It changes the dynamics and it makes for more equality in who turns out to vote. In terms of the quality of the vote, it's really an arbitrary judgment to judge what is a good vote and what is not a good vote, what is an ill-informed vote. There are lots of reasons that could motivate people to pick a particular candidate or to pick a particular party, and there's no way we could decide what is a correct vote and what isn't.
There might be a bit more noise added to the system if you're requiring everyone to turn out to vote, but then again, it doesn't change the electoral results. In that case, the equality argument's really the more important one.