I would vote the B24 (with bias since my dad worked on one in Italy). It was built in more numbers than any other aircraft and could carry the same bomb load higher, farther and faster then than the B17.

B29 Superfortress?

Well my father in law was a master mechanic on the B17 in WWII and even though they made more B24's and it done what you said, the B17 was a good plane. Anyways how about the British Lancaster? I believe that carried more then either the other two mentioned here.

Joe

I guess like the fighters it is hard to pick the "best". Perhaps "favorite" would be better wording. The Lancaster was something else. I really liked the dam buster drops. Took some seeds to fly those missions.

I read about the Lancaster and that plane was built for one thing, bombing, thus no creature comforts went into it at all. The crew was cramped and pretty much nearly froze to death. The plane was able to carry a large payload and it did carry some really big and heavy buster type bomb too. I think it had both 303 and 50 cal guns on it. Something like that.

"Best" may be a tough one. They were all so good at what they did. My order of preference would be the B-17, the B-24 and the B-29. The 29 last because of its limited period of service, and only in the Pacific. I crewed on one in the late 1950's and even then it was quite the bird. It remains my favorite.

What was the best American heavy or medium bomber of WWII (actually used in combat) and why? 'Best' all around or 'Best' for a specific mission or purpose? This could also be for a variety of different situations or missions. Think about it this way, which one would you entrust your life to? What if you were in charge of a bomber group and had to worry about things such as availability, quantity, reliability, payload, sortie rate, etc.? What if you were in charge of production and had to worry about production cost, volume and quality? Probably many other ways to look at this too. I think this would be more difficult than selecting the ‘Best’ fighter, certainly more so if you weigh the cold, hard facts against the personal preferences. Also, I see quantum leaps in the design and performance of the various bombers from say, 1940 through the end of the war – it is certainly a long way from the B17 to the B29 and I personally think that would be the ends of the spectrum. Only the US and Brits, in my opinion, had a true ‘Heavy’ bomber – but the smaller, twin engine bombers carried a lot of the load and did many things the bigger bombers were incapable of – witness the Doolittle raid on mainland Japan with the B25’s launched off a carrier- what other A/C could have done this? And all of the bombers mentioned had flaws, some of them very serious flaws. The B17 & B24 were miserable A/C to serve in as they had no heat, forcing the crews to wear heavy clothing and electrically heated suits, the Lancaster served a purpose and served it well but had many of the same problems. For pluses, the old B17 was a very tough airplane and brought home a lot of crews even when badly shot up, the Lanc had the advantage of a tremendous, uninterrupted bomb bay allowing it to carry very large, bulky bombs. And we could certainly continue this debate, probably for a long, long time.
Any argument becomes a moot point if the bomber was not effective and the US had an edge here, not so much due to the A/C being flown but to the great effectiveness of the Norden bomb sight which allowed better placement of the bombs being dropped. My, my this is going to be a bloody argument, I can see that now!
My personal vote would have to go to the old B24 and I have personal reasons for this.
Overall, I believe the B24’s shouldered up to the load probably better than any WWII aircraft although that is certainly arguable, and for a fact there was a lot of them.
And then again we must consider what exactly we are looking for: Heavy bomber, medium bomber, dive bomber, fighter bomber – all had a place and served a purpose. Daylight bomber or night bomber o ran A/C suitable for both roles. I believe the B29 was the first A/C to be termed as a ‘strategic’ bomber whatever that means.
If we look at all the pluses and minuses, the B29 absolutely has to be the ‘BEST’ bomber of WWII. However, it came late in the war, serving basically only in the Pacific and it did drop both the “A†bombs on Japan. It had advantages in range, payload, altitude, speed, crew comfort, etc., etc. In fact, I can think of no single area that the B29 did not in fact outstrip any other bomber used by anyone in WWII.
I'm very curious to see where this thread goes, what info we find posted.

The B-29!

I thought about this one a while. My vote goes to the SBD just because it was in the right place at the right time...Midway.

As TrapperP says, it's difficult to pick a winner, but regarding the heavies, I'd agree with the B-29. But the light and medium bombers were very effective also. Don't forget the truly remarkable Mosquito...