Is it ok to say "my [or his or her] advantages"? Or should advantage be used only for non-sentient subjects, for instance, "advantages and disadvantages of a company"?
It’s OK to speak of practically any entity, animate or inanimate, corporate or individual, physical or mental, as possessing or offering an advantage.
But when you start playing with prepositions you have to be careful.
Keep in mind that five distinct entities are involved when you speak of advantages.
First, there is the Benefactor—the entity which provides the advantage. We usually speak of this with of: the advantage of speed, the advantage of access to markets, the advantage of wealth.
Second, there is the Beneficiary—the entity which enjoys or wields the advantage. We usually speak of this with to: the advantage of speed to a predator, the advantage of access to markets to an enterprise, the advantage of wealth to a student.
Note that either of these first two may be expressed with the genitive: speed's advantage, or the predator's advantage.
Third, there is the Domain—the entity within which the advantage obtains. We usually speak of this with in: the advantage of speed in hunting, the advantage of access to markets in increasing sales, the advantage of wealth in getting a good education.
And fourth and fifth, there are the Rivals—the entities with respect to which an advantage is asserted. Rivals are of two sorts, rivals to the Benefactors or rivals to the Beneficiaries: either one advantage is superior to others, or one competitor is superior to others by virtue of enjoying that advantage. We usually speak of this with over: the advantage of speed over strength in hunting, the advantage students from rich families have over students from poor families.