With the option to speak with the dead about how you get to each type of afterlife, as well as what it's like, people would probably do some research and what each is like.
And then, their conclusions might not be what you expect.
Because on the face of it, heaven seems better than hell, but that's because we discount the "eternal" part. In reality, once people talk to some of the long dead people, they will reach one of two realizations:
1) You are still your normal self in heaven, but forever. This is horrible, because our minds and bodies aren't capable of properly coping with the idea of forever. Imagine talking to a person who has been in the same place, experiencing the same thing, for a thousand years (or more..)
If you think your regular job is drudgery, wait until you live a thousand years doing the same thing. Without a sense of finality, a sense of danger or a sense of challenge, your "life" will be quite dreadful. Heaven would sound dreadful. (Probably, so would hell, I don't know which would be worse.)
After genuinely talking to someone who had been stuck in heaven for thousands of years, most people would dread the idea of going there. I'm guessing the vast majority of people would become severely depressed. The idea of immortality sounds like a worthwhile goal, but when you really think about it, it's horrible.
2) You turn into something capable of coping with immortality. This would be pretty apparent when talking to these dead, and given that they cannot lie (when it's pretty fundamental to most people to lie from time to time) it's the more likely scenario in your description.
Now you have another problem, because once people start to disassociate themselves from the dead, they also start to feel like it's not "them" that will go to the afterlife. If you've talked to your dead parent, or spouse, or sibling, and you cannot really feel it is them, then what makes you think when you die the thing going to the afterlife is you?
They will instead be condemning something that vaguely resembles them to it, but that will cause them to care a lot less. We might think that we are good and decent people, and we wouldn't condemn other people to such a terrible fate, but when you look at the world we don't really care all that much about those we don't know. Most people vaguely, subconsciously realize that if you buy an iPhone, it was probably built by a child-worker, and that we're slowly destroying the Earth with our consumerism, and that animals have feelings and we're brutally killing them for food, but for the most part we just don't think about it. Because when presented the choice between a delicious cake, or a meal for a hungry child, most people will pick the former unless you're making a conscious effort to appeal to their better nature. (Because most people don't realize that if you donate the cost of the slice of cake, you could easily use it to feed a hungry child. Any time you eat cake, you could have fed a child. If you pick the cake over the child right now, why would you pick the cake over the thing going to heaven or hell in this other world?)
Once people start caring less about what they're condemning to the afterlife, likely their normal sense of self and morality will take over, and you will end up with mostly whatever you had before people realized the truth of what happens after they die.