Honestly, I wouldn't want to know either of them. But if I had to pick one, I'd rather know how rather than when, solely for the fact that it would be way too depressing to know when I was going to die. I think I'm less likely to live my life in fear of when I'm going to die than to live in a general malaise from knowing exactly how long I have left.
Good points, though I guess it all depends on the rules of this clairvoyance and the destiny, or lack of, surrounding it.
Knowing how can be worse than knowing when. For example : Knowing when : You will die 10 years from now. Well, at least you may have 10 years. Knowing how : You will die in a vehicular accident. So, now what? Everytime you are near traffic or get into a car, you'll be thinking you're a dead man. On the other hand, knowing when you will die may not tell you anything either. For example : You will die in 2 years. The next day you get into a car accident that puts you in a coma for 2 years, after which you die. lol. Oh, btw, I'd choose "when" over "how". Who cares how you're going to die? You're going to be dead anyway.
People aren't reading the premise carefully enough. It's important to note that you would only be told in a very general way how you would die. For example, you would might be told "accident" or "disease", but not "car accident" or "AIDS".
Due to my religious beliefs, I have a very non-carpe diem attitude: that worldly things are fleeting, but rather than only focus on the here and now, look beyond. So if ClutchCityReturns is right that the "how" answer is ambiguous, I'd pick that one. Mine might read something like, "you'll die because you were naturally selected against" or "wrong place, wrong time". Even if it were specific, that'd be ok. If I knew A, I could still live with it. But, my friends and families wouldn't understand since I wouldn't keep this knowledge from them. When I marry the woman I love, I want her to assume that I'd live for quite a while, that my children know I'm coming home to play with them after school, that my parents won't live to see their child buried, etc. What they don't know, won't hurt them. Thus, to spare them the melancholy of my exact impending death, I'd pick B.
As stated above, there's also murder, suicide, and old age. Not to mention natural causes (heart attack, starvation, hypothermia).
I would choose B because I would never want to know the year of my death as I'd be counting them down. Imagine if I picked A and it said 2014...I'd be devastated. Now instead I'll pick B and it said "natural causes", while I might still die in 2014, at least I won't be traumatized from now till then.
The year. That way I can go do something incredibly stupid (and hopefully deadly) the day right before my ensuing death date.
Ahh, but that's too simple. Consider this hypothetical... So what if you're told that you'll die in 2020, and on the last day of 2019 you go do this incredibly stupid thing and end up nearly destroying your body. I'm talking a laundry list of broken bones, as well as scrapes and gashes everywhere...terribly painful. You're hospitalized for months, and once you recover you can hardly walk and your face is mutilated. No decent looking woman will come near you and your general quality of life is at an all-time low. And it turns out you don't die until December 31st, 2020.
Knowing one of both would really mess a person up psychologically. But if I had to choose, I'd go with the time. Maybe an exact countdown to the very last second. I'd probably join the military and go out with a bang. Would be a drag though if I found out I won't go for another 50+ years. I'd be well into my 70's and life would probably be pretty boring way before then.