Better athletes? I never said that.
Tougher individuals across the board? I don't see how anyone can dispute that. Your average baseball player could never, ever endure the harsh pain NFL players have to endure. They wouldn't last.
It's sad that Linemen in this day and age have to be at least near 300 lbs, but if you want to keep up with the league it has to be so. They don't run more than 10 yards at a time, but in their 3 hour game exert a of a lot more energy and effort than any baseball player. The catcher gets some bumps and bruises and may get a collision at home plate every now and then, but linemen get it dozens of times a game. The only grueling thing about baseball from the players perspective is having to stave off boredom for a ridiculous 162 games a year.