As has been said, Route A is the fastest and the cheapest; that's a pretty powerful starting position in any public sector options appraisal (this may even explain why it is presented as Route A....!)
FWIW, I prefer Route B South a northerly approach over the (replaced) busway. But for this option to be chosen, it will be necessary to explain why spending more for a slower journey time is worth it (direct service to Science Park, lots of homes in Cambourne, extensions to Stansted, options to St Ives/Huntingdon/Chatteris I believe does it) but be under no illusions about how hard getting away from Route A will be.
FWIW, I prefer Route B South a northerly approach over the (replaced) busway. But for this option to be chosen, it will be necessary to explain why spending more for a slower journey time is worth it (direct service to Science Park, lots of homes in Cambourne, extensions to Stansted, options to St Ives/Huntingdon/Chatteris I believe does it) but be under no illusions about how hard getting away from Route A will be.