1440 or 2880 won't change the amount of ink being laid down by more than a fraction of a percent and it certainly won't make a printer visibly darker.
Generally, unless you have very fine diagonals or super fine detail and a suitably high res input file (720ppi), then 2880 shouldn't provide any particular advantage over 1440, but will take longer.
Most people, including most photogs, wouldn't spot the difference between 720 and 1440 or 2880 on a lot of prints - certainly not without a loupe.
That all said, if you have no particular time concerns, then 2880 may give you some improvement without giving you any downside apart from time taken.