The ‘benefit’ of a leadership challenge depends on which side of the fence you are on.

For Mrs May and her supporters and/or supporters of ‘her’ deal the potential benefit of winning the vote of confidence is that it makes her ‘safe’ for at least year - well after the scheduled Brexit date and much of the transition period for any deal.

For her opponents the big ‘benefit’ if she does lose the vote is that the Brexit date will almost certainly be delayed.  A delay will give the ‘remainers’ within the party more time to manoeuvre for a second referendum and for the hard Brexiteers to push for an exit with no deal.