Well the two most obvious answers are that the British don't lose thousands of troops to disease, death, or capture, and avoid a very large embarrassment. Neither Townshend or Nixon, or to lesser extent Lake, seem to have been very on the ball which makes me think that even if the siege had been avoided they might well have found somewhere else to have a disaster later on. Granted he had more time and resources but IIRC the main strength of Maude was that he systematically improved the logistical and medical systems for his forces putting them on a more solid foundation. I'm not sure if it would of had much effect on the Sinai and Palestine campaign considering the distances involved, at least until Baghdad was captured and the rivers then offered a potential transport route to move Westwards.