aka b29
Once they worked the problems out of the 3350, the engine was a reliable, powerful, and effective one. Like almost every other engine you ever come across in ANY aviation, the engines go through trial and error, and therefore, improvement.
And you're really talking about apples to oranges. The B-29 became a workhorse alongside the B-17 and B-24. Eventually dropping Fat man and Little Boy, they dropped incendiaries on major Japanese cities before then. The B-29 was a vastly more effective and widely used aircraft than the 177.