Salah, fairly easily.
It's a pretty simplistic point but there's nothing you can really do on a football pitch that has more impact than scoring goals and Salah's goalscoring peak was a 32 league goal season. And if you want to take consistency over multiple seasons into account, he's had six 19+ goal league seasons in a row. Whereas Hazard maxed out at 16 league goals and never had more than two consecutive seasons hitting double figures.
And even in terms of assists, Salah's output over multiple seasons holds up well against Hazard's.
Salah: 10, 8, 10, 5, 13, 12.
Hazard: 11, 7, 9, 3, 5, 4, 15.
Salah with twice as many double digit returns in one fewer season.
Hazard was quality and offered more to his teams than just output, but then Salah isn't without his own value beyond output either. I think pretty much every manager would opt for peak Salah if given the choice between the two, as there's just too much value in that consistent material impact.