Statistically wise, Donaire has all the advantages over Santiago.
Some of these are height advantage, reach advantage, better KO percentage, much faster, much quicker, having a strong punch, good at counter-attack, versatile, agile, better footwork, and what else, much good looking, just kidding.
Santiago should not be a problem for a 40-year-old Donaire since Moloney, the supposed original match is even considered much tougher than Santiago.
The records of Donaire is already a stand out as a bantamweight, and then those advantage that you also mentioned.
But we shouldn't be overconfident that Santiago is not going to be a problem for Nonito, in boxing all is needed is that one punch to change the tide of the game. So Donaire will still need to be very careful, so that as fans of him, we will be happy to see him winning another belt. Of course Moloney is much tougher but they don't want to pursue Nonito for many reasons and so chooses a very easy route to another belt in this weight class.