I'm kind of torn between the top deck and the nose seats.
I've flown British Airways's business class on the upper deck, and I've flown Qantas' business class which is all on the lower deck starting at the nose. I wasn't quite at the front, but I was close enough to see the slightly more forward facing windows. I always thought it'd be great to sit in that first row and have that more forward facing view.
I had a blast on BA's though, as I was young and blowing through a bunch of airline miles on a transatlantic flight with my now wife. Getting to sit backwards on a plane was a little fun change too. Those BA seats (their last generation business class) are pretty bad by business class standards, even at the time, but they were alright on the narrower upper deck of a 747.
It's a shame, as I don't think I'll likely ever fly in a 747 again. I rarely fly Korean Air or Lufthansa, and I've got no plans to fly Air China.
I will say though, I really didn't like flying the 747 in economy. I did with Qantas a couple times, and it was noticeably louder and less pleasant than their A380s which had started flying at the time.
So my recommendation: fly a 747 at the front or upper deck if you can in business or first, at least once if you've never had the chance. Avoid it if you're flying economy. Most other wide body jets will be newer, quieter, and all around more pleasant.