Does being an informed voter always lead to good outcome?
You need to define terms.
- What does "Good" mean?
- What does "Informed" mean?
- What does "outcome" mean?
But to clearly answer your question:
Informed according to who?
It basically comes down to who you believe. The data suggests that the number one driving factor for Americans is Partisanship. In short, one group of people have a certain value and another group has theirs.
It basically boils down to values, not facts or truth. Both parties promote specific policy positions and citizens either support them or not. Data might prove one position or another wrong, but that's generally irrelevant.
The basic truth, is there are many citizens who don't care about the data. Many people would prefer policy that reflects their values and worldview rather than the most "fact driven" answer. This is mostly because humans are creatures of emotion and empathy.
Why do people spend so much time and emotion attempting to apply their own moral sense to an animal’s actions? The answer lies in the human capacity for empathy — one of the qualities that helps us along as a social species.
When we are confronted with another person — say, someone in pain — our brains respond not just by observing, but by copying the experience. “Empathy results in emotion sharing,” explains Claus Lamm, a social cognitive neuroscientist at the University of Vienna in Austria. “I don’t just know what you are feeling, I create an emotion in myself. This emotion makes connections to situations when I was in that emotional state myself.”
... and this is VERY important to democracy. Because it might be efficient to cut spending to help people... and sure, it'll help the budget. The numbers would play that out. But in reality, it doesn't work that way.
So, the issue "We need to save money."
The government responds with a cut to veteran's health care.
The population doesn't want this and will support policies helping veterans.
Fact, cutting spending will help the budget.
Sure, we KNOW making cuts saves money. But our values say, money isn't as important as the well-being of veterans.
That was a very general easy example. Abortion is a far more complex issue. Because of the interlinked issues of science, religion, history and women's rights.
... and there's a whole host of issues like this. The short answer is, people know enough to vote. People, on average know enough. This question assumes that all we need is "knowledge" and that will provide outcomes to the positive. That's simply not the case. Issues are more complex than Facts.
I'm saying your terms are vague and more importantly imply that "knowing" is enough for a democracy to function. It isn't. Engagement is likely the strongest indicator of a successful or "Good" democracy.
To quote the Center for American Progress
For the nation’s democracy to function properly and for government to provide fair representation, all eligible Americans must have the opportunity to vote—and be encouraged to do so. Our collective self-rule is established and fostered through free, fair, accessible, and secure elections through which the voice of every eligible American is heard.
If a minority of citizens vote and a majority stay home, then a minority will decide policy. At the end of the day, engagement is everything.