They're 2 different type of players imo. Atleast in my save, playing as Valencia, I have Maia. I use him as a DM-BWM(S). Cubas plays for PSG in my save, but looks more like a DLP. Both are quality, though.
Bought both for Benfica, already had Renato Sanchez and then Hojbjerg got transfer listed so have 4 of the best young mid's in the game!!
But as for your dicsussion, Maia has been so reliable as a Ball Winning Mid Support and Cubas has been decent in that role and as a Box To Box...If I was to pick one it would be Maia though