There are no true proofs outside of realm of math at all.
SpaceX odds for going to Mars are, however, better than anyone else's.
SpaceX odds for going to Mars are, however, better than anyone else's.
NASA, for example, has done that multiple times.
So why exactly are SpaceX odds better (@ succeeding)?
That rocket landing to the platform flying backwards looks awesome but I don't think it significantly increases their odds for Mars flight. Will they fly there backwards with a similar platform waiting?
As for what SpaceX (and OrbitalATK) does better, look at the cost of ISS cargo deliveries, and then read about the history of Constellation and Ares.
So far SpaceX delivers, and unlike every other player out there, going to Mars is their core mission. So yes they odds are much better than anyone else's, even if by the virtue of none remotely competent pursuing it at all.
Otherwise sending a drone to plant a plaque on Mars has certainly been possible for SpaceX for some years now.