And the difference is? Syntax, not semantics. Light years of difference between only the elect "could" choose to accept and only the elect "will" choose to accept it.
It all stems back to "total depravity."
Romans 2:14ff
When the Gentiles, who do not posess the law, do instinctively what the law requires, these, though not having the law, are a law to themselves. They show that what the law requires is written on their hearts, to which their own conscience also bears witness; and their conflicting thoughts will accuse or perhaps excuse them on the day when, according to my gospel, God, through Jesus Christ, will judge the secret thoughts of all.
There is a light-year of difference between the two, to be sure.
Why do people reject the gospel? It's because of their nature: we love darkness rather than the light. Only because God intervenes in some of our lives, changes our values so that we are willing to no longer rebel, but submit to him, do any repent.
It's all about "could." The natural man cannot comprehend the things of God, because they are foolishness to him, because they are spiritually discerned.
Do you understand the theme of Romans 1-3?
Paul lays out that men can not be saved apart from Christ. He gave the Jews the law on tables, he wrote the law on the heart of men . No man can keep the law ( on his heart or on the tablets) perfectly. All men have fallen short of the glory of God, and need a saviour ...
Gal 3:10 For as many as are of the works of the law are under the curse: for it is written, Cursed [is] every one that continueth not in all things which are written in the book of the law to do them.