Hardly seems a contest in truth. They might be similar for talent but Salah has turned into a ruthlessly productive player. He could probably play in any system, whether it is relentless pressing or counter attacking football. I don't think you have to cover him, or make allowances, he's simply a brilliant attacker.
Hazard was brilliant to watch and had excellent seasons, and particularly incredible stretches of shorter term form. But what it comes down to is he just wasn't as interested off the ball or when it's not to feet. That's where a manager would probably always pick Salah because the small margins matter for the team. Also you cannot really argue against Salah's output which is way more important than dribbling ability. Hazard might get you 10 goals, Salah will threaten a golden boot and win you a title in the process.