While having multiple nominations can be beneficial if your name ends up on two lists - I can't see any benefit at all for having two presidential nominations. This would be redundant and a waste of resources to even apply for two.
There is ONE list from which the Presidentials are apppointed - they are selected by merit and either you make the list or you don't.
This is why it's important for those who have a Presidential to also seek MOC nominations.
So, if you weren't in "their" top 100, it prob ably wouldn't matter if you had 1 or 5 presidentials.
Don't de discouraged. This is not true. Many, if not most, of the top 100 will also receive MOC nominations and, subsequently, appointments from these sources. Consequently, the appointments from Presidential nominations will work well down the list to those with no other nominations who truly need them.