There is an excellent analysis on the BBC here http://bbc.in/21a1u9n
The basic points are as follows.
The government want a 7 day NHS but will not increase spending even to cover the increasing demands on a 5 day service.
The costs of a 7 day NHS for each year of healthy life expectancy gained by patients are enormous and more could be achieved by spending the money in other ways, according to an economic analysis by Manchester university.
The reasons why patients admitted to hospital at the weekend are more likely to die than those admitted in the week have not been investigated. In spite of this, Jeremy Hunt has repeatedly told parliament and the press that the junior doctor’s contract is the answer.
When asked to comment by the producers of the programme, he refused.
From my perspective (I haven’t been a junior doctor for over 15 years) no matter what the terms and conditions of the new contract stipulate, the abject failure of the government to provide an honest justification makes it impossible for the BMA to accept it.
Update 06/05/2015 New study shows weekend staffing doesn’t affect mortality http://www.independent.co.uk/life-style/health-and-families/health-news/seven-day-nhs-jeremy-hunt-staffing-hospitals-weekends-junior-doctors-strike-a7016286.html