I'm not going to do anything original or creative with these options. As such, the shark is the Bad (BLOOD IN THE WATER) One, and the Dolphin is the Good ("Pardon me, but does your ship need saving?") One.
So which one will you meet when death Comes For You? Obviously, it depends on whom you're going about asking. Those without belief will unerringly go for the shark. It's vicious. It's unerring. It's kind of cool. It will eat you without compunction and then go off to find a momentarily unguarded cephalopod and eat that as well. When death is an encounter with a shark, it means nothingness, extinction, no one being able to hear you scream if you were able to scream anymore which you emphatically are not.
And then you have the dolphin. Ah, the dolphin. Super-intelligent, but somehow not cool because of all the tween girls and "spiritual" adults with dolphin tattoos and necklaces. The dolphin death people are those with a belief in some kind of benevolent post-death experience. You run into the dolphin (death, in this analogy - follow closely, won't you?) and it greets you with smiles (really not a smile, just a physiological characteristic, but in this analogy, it's a smile) and friendly guidance. "Come with me," it says. "I'm like the boats at the end of Lord of the Rings. I will take you to another country. I will not eat you up like that son of a bitch Shark."
So which death scenario is correct? Do we believe in the cool, sharky atheists, or the friendly pious dolphins?
I believe in neither. Because both are based on some kind of faith. If we have a problem in mathematics, we can go and see the best mathematician and he (field still largely dominated by men, alas) will either give you the answer or tell you to get the hell out of his cramped bungalow. Ditto business (except for a far larger house)...English literature (although all answers will be provisional and totally unhelpful)...medicine (actually, still many advances to be made, but my point is that advances CAN be made)...but have a question about death, and where can you go? Whom can you ask?
"Oh, see a priest," someone would undoubtedly say. And the priest would tell you what he (field still largely dominated by men) really BELIEVES will happen. "Oh, see an atheist with a book on the New York Times bestseller list," someone else would undoubtedly say. And the atheist would tell you what he (it's either Hitchens or Dawkins) really BELIEVES will happen. They don't know anything. Both belief systems are BELIEF systems. There is not an expert in the world who can give you any real insight into death. The smartest people who have ever lived would be unable to help us because they are either alive and therefore cannot research the subject, or they are dead and can't publish the research.
So choose: shark or dolphin. You have a 50/50 chance of being something close to correct. Or do what I do and choose neither. That way, you can spend the rest of your life haunted by your own ignorance and the malign mysteries of the world.