hmmm... of course I don't KNOW why their opinions differ that much, but I think it has to do with their experience with simulations.
I think if you don't have gaming/sim experience at all, you're more likely not to find a certain sim very realistic among other things for the most obvious reasons: pedal-feel, steering-lock, G-forces, FOV.
Imagine Fangio testing LFS...
. I think he'd say it's complete crap.
A person used to the obvious limitation of a PC-based simulation will not even care about these. It gets second nature, somehow. However, it is not like in reality.
We're used to these limitations, so we can make somekind of link to the real thing, and we can enjoy the things that are modeled pretty damn well (like LFS's physics engine... with exceptions).
Maybe Glock is more of a simmer than Heidfeld. Therefore the fairly different opinons.
I still think that Heidfeld's rating has more value. Because - to put it simple - if the game was extremely close to reality, the best real driver should be the best sim-driver even without the tiniest bit of practice with the sim.
So if the general opinion is "Heidfeld hasn't practised enough" then that's an indication of the sim not being too realistic.
I hope you understand what I mean. Kind of hard to explain this in a foreign language.
This all reminds me of the late 80's, when I was playing Test Drive with a digital joystick.
"Hey Dad, you wanna drive the Lamborghini?"
But Dad couldn't drive at all.
With a very realistic sim, Dad should have been better than lil' Kiddo right from the start, even if 10-year-old Kiddo had been practising for some days.
Would this be the case with LFS? I do not really think so.