My point of view here, hoping to light up the debate (lighter style, not flamethrower style
)
It seems to me that LFS follows a unique path, trying to simulate car physics as accurately as a computer game can do it.
On the other hand, ISI and iRacing seem to aim at simulating how a car feels, as accurately as a computer game can do it.
Both ways are equally correct, however the limitations induced by the sim being only a computer game have a different effects on the user, with different shortcomings especially during development phase.
I see LFS development as being a more hardcore / purist way, like high level maths are a form of art (abstract art I must say). ISI - iracing way is probably more efficient and to the point, and in the end when these sims have reached maturity the difference between them will probably be barely noticeable.
I am more interested in the LFS way - it feels like an incredible piece of software, but I am also sure that it is not following the most efficient way. Long years enjoying the path forward ahead, why not?
If we ever get bored on the path forward, we can jump on the rfactor - iracing wagon, and get comparable or faster progress. We will probably all come back here later though