You know I looked at the first pages of this thread and it seemd like tere was a pretty good battle going on between some people in here.
So I looked up some numbers for the entire war and came up with the following:
1) Lancaster: Bomber sorties: 148,403 (not the 156.192 for all sorties) , losses: 3,832, loss / 1000 sorties: 20.8, tons bombs: 608,612, tons / sortie: 4.1
2) B-24: Bomber sorties: 226,775 (in Europe, 1942 - 1945) , losses: 3.626, loss / 1000 sorties: 16.0, tons bombs: 452,508, tons / sortie: 2.0
3) Hallifax: Bomber sorties: 73,312 (not the 82,773 for all sorties) , losses: 2,232, loss / 1000 sorties: 30.4, tons bombs: 224,207, tons / sortie: 3.1
Please don't quibble with the numbers unless the changes are significant. If not significant, the general stuff that follows won't change.
So, it looks to me as if the B-24 is the safest to fly on a combat sortie but not by a great margin, the Lancaster delivers twice the bomb tonnage per sortie, with the Hallifax being more dangerous to fly per mission but still delivering more bombs per sortie than a B-24.
As a Prime Minister, I'd opt for the Lancaster for bombs delivered. As a crew member, I'd opt for the B-24 as safer but, again, not by a large margin ... could go either way. For maritime pattrol, I'd opt for air cooled engines as not susceptible to failure due to coolant issues. For other missions, I'd probably take the Lamcaster for per-mission effitiveness (bombs per sortie).
After the war, the B-24's were taken out of service, not due to any aircraft shortcomings, but due to not needing a huge strategic air force after the war was over. We weren't going to be bombed anytime soon by anybody, as far as we knew. We still had B-29's (perceived as our best bomber, and the war's heavyweight champion) and B-17's (very well though of) if needed, plus a few medium bombers to fall back on. Really, we didn't need 3 or 4 types of heavy bomber in 1946. Likewise, we retired a lot of piston fighters while still keeping a few types around, notably Mustangs and Corsairs.
The Lancasters were kept in service because there were still a bunch left after the war and it was perceived, not incorrectly, as the best British heavy bomber of the war still in service. The Brits needed SOME bomber, why not choose their best one? We did! The British loved Lancasters like we loved the B-17 and flew them until the first-gen jet bombers were in service. They gave yeoman service and did everything asked of them.
There was no hatred of the B-24 after the war, it became superfluous to the military needs of the USA and was removed from service as a simple economic result.
I didn't post this to restart a fight.
I think both planes did very well in the war. The Lancaster unquestionably carried more bombs per sortie, but wasn't safer in combat or as long ranged. But if you needed to fly a mission that was outside the normal range of the Lancaster, you could drop the bomb load and add fuel or take B-24's. I believe the British did both as dictated by the situation at the time and resources available to the commander.
While I am American and feel I shoud, "take up the cause" for the B-24, in reality I am also a Lancaster fan. Looking at it from a hopefully unbiased viewpoint, the USA had more heavy bomber types to choose from. We had the B-29, the B-17, and B-24. The B-25, and B-26 were also available for some missions. The P-38's could be presed into carrying bombs too, as could any number of fighters, but not much bomb load.
The British had the Lancaster and Hallifax. The Short Sterling wasn't a great success and neither was the Whitley or Hampden. So they really had two heavy bombers and several great ships like the Mosquito and Beaufighter / Blenheim that could be pressed into being medium bombers, but they generally had fewer choices. It happens when you get bombed on a regular basis during several years in a long war. Part of the reason the US had more choices and more production was lack of attack from above by anything heavier than pigeons.
All in all, I think the British made their best choice after the war was ove in keeping the Lancasterr, and so did the USA in keeping the B-29. We were still flying B-29's well into the 1960's, about as long as the faithful Lancs served England and went on serving in the guise of Shackletons into the 1970's. People may SAY the Shacks weren't Lancs, but they were close relatives if not, and also did great service. Neither type need be embarassed of the war record and both were good planes for what they were asked to do at the time. I think the Lancaster was better on a one-on-one basis, but there were a LOT of Liberators in the theater. Was a Lancaster better than two Liberators? Maybe, but I don't think by a large margin. And we had both Lancasters and two Liberatos per Lancaster available. Life was good for a commander who had those options!