DHL regularly operated the A300 on routes from BRU to LOS and BAH; to BAH with the odd fuel stop in LCA but capable of non-stop with reduced payload.
Although the max payload on the A300 is above 40 tons, DHL rarely utilies this as they aircraft are full by volume around 35 tons.
The A300 was brought in as the replacement for the long diesel 8s, and offered more payload, much more volume and considerable operational savings. Yes it's a 3 crew kite, but the alternative would have been the A300-600, which are much more expensive and not readily available second hand in the sme numbers as the B4-200. DHL does not buy new. In short, the A300s offered DHL the only viable growth potential, and continues to provide excellent service.
The B757SF and A300 uses the same ULD types and therefore compatibility from a cargo point of view is not a problem. Obviously the 757s won't accept the widebody lowerdeck ULDs. And as with the A300 DHL will normally not be utilising the full 28 tons capability of the B757SF, but will top out on volume around 23 tons.
So Myrr, we're happy with both the A300 and B757.