Better speed, range, altitude, bomb load, bomb sight, and defensive armament than the Lanc. And, by the way, was pressurized. B-29 was the best of the war.
The B-29s were already carrying H2X. And that equipment was required to fulfill the Lanc's mission. The B-29 was a daybomber and didn't require all the gizmos.
The B-29 was the newest so yes it could be the best. But then it also did not have to fly through a lot of the fighters that the B-24s had to in Japan. I would have loved to see how it could have worked say in 1943 when the B-24s were fighting off fighters. 8)
It is Mrs. Roosevelt. I think the B-29 would have handled itself very well in the raids of 1943. In had more (and more accurately aimed) guns. I'm not claiming it could have flown into Fortress Europe unescorted without losses, but it would have done at least as well as the B-17 and B-24.