The grass is always greener on the other side. Men, who are scared of the great unknown, despise the gift of Eru Ilúvatar and crave the immortality of the elves. Elves fade and grow weary of the world, so they become envious of the death men get to enjoy. For both these races, there is general desire to have what they cannot, but that is the nature of life. In the legendarium however, there are several characters who get to decide their fate to some extent, but they do so not out of the fear of death or the weariness of life, truly making them the masters of both. Both men and elves consider the other the luckier of the two, and they grow to dislike the state Eru has put them in.
In the legendarium, the race of men has constantly been motivated by the fear of death and the unknown. It has been what motivated their fall time and time again. The most glaring example of course is the fall of Númenor. So terrified of the thought of dying are the men that they declare war on the Valar and set sail for Aman, which is strictly forbidden. They also begin to commit human sacrifice and to worship Melkor. This all leads to Eru sinking Númenor beneath the sea. However, the men of Númenor were not always this way. Númenor was originally given as a gift to men for their brave services in the War of Wrath. Men also enjoyed extended lifespans at that time, long enough for them to grow weary as the elves do and pass from Arda gladly. The lifespans shortened though, and men no long tired of the world. This sense of being cheated of eternal life stems from a place of ignorance. They do not know the toll endless time takes on a soul, so they do not fear it. They only fear the inevitable unknown. The lack of agency and unavoidableness of death is what leads the men of Númenor into revolt and destroys man.
The wiser elves see more clearly than the short-sightedness of men. The elves, who endure the entirety of the world, grow very exhausted of it. Thousands upon thousands of years takes its toll. The elves also undergo a unique process of fading, which can only be halted by the departure to the West. This fading is the physical manifestation of time on the elves. Reminiscent of the Ring Wraiths almost, the elves slowly fade into spirit. Though they lack the malicious intention of the Wraiths, the principle is the same. This fading was not always the case, but came to be only after the War of Wrath and Melkor’s final defeat. This signaled the decline of the elves and rise of the age of men.
Here, discussion of the merits and misfortunes of elfish immortality must split into two: the elves who always remained/returned to Aman and those who yet remained in the Middle Earth. The elves in Aman, whom we do not hear much about after this point, live on in supposed “bliss.” It is an interesting characteristic of the Children of Ilúvatar that they become bored rather quickly with what they are given no matter how wonderful and beautiful. As the Edain tire of Númenor, so the elves tire of actual paradise. The elves of Aman therefore are forced to live out the length of the world in a dystopian Eden, waiting for the world to end. It seems that the opposite of the Gift of Men is the Curse of Elves.
Even the valiant souls of the elves of Middle Earth cannot overcome the effects of time, but can merely prolong their effect. Galadriel and her ring in particular epitomize the effort to fight nature, but even she realizes it is a losing battle and gives up. While men and their fëa get to leave the world, elves must watch as theirs slowly fade into darkness. The theme of fighting one’s nature is universal to the Children of Ilúvatar. Both grow to hate their fortunes and envy the other.
In Athrabeth Finrod Ah Andreth, Finrod and Andreth debate the merits and inherit issues in elfish immortality and mannish mortality. Both try to convince the other that they are suffering due to a curse placed upon them. Andreth states that originally men were also immortal and some menacing spell of Melkor stole this extended life away from them and cursed them with death. For men the Gift of Men will always seem to be the Curse of Men. Finrod explains the tethering to Arda for its entirety, which shocks Andreth.
Elros and Lúthien both choose death. While Lúthien does it for love, Elros gets to experience what elves have always envied. His ability to depart the world after a significant enough amount of time to grow weary of it might make him the luckiest of the Children of Ilúvatar and the one who experiences the wonders of Arda to the fullest extent because he does not tire of them.
Athrabeth Finrod Ah Andreth perfectly encapsulates the man vs. elf argument. It is two creatures bemoaning their fate and desiring that of the other. The conversation is also not the matter of poor communication skills in that they are listening to the benefits the other is describing. Finrod hears Andreth’s claim that immortality is to be desired and Andreth hears Finrod’s claim of the opposite. Time and life has switched their perception. What Andreth views as a curse, Finrod can only view as a blessing, and vice versa.
I personally would choose the Gift of Men. The elves have a sense of defeat in the later ages that leaves nothing to be admired. In addition, though men always will have to live with the shadow of death upon them, it makes men appreciate the world in a way I believe the fading elves forget.