It's quite difficult to be able to say outright that PS1 and PC should be separate, but there are some differences that can argue for the separation.

For one, due to less constraints for PCs, the PC version has a lot more traffic, and therefore it is harder to manoeuvre through levels without crashing into cars. On an added note to this, the damage boost in 'The Getaway' is much harder to pull off, as there is less space to drive through the traffic jam. Another thing about traffic is that, with more traffic, it becomes easier to evade police because police AI is pretty crazy and so will crash into cars more frequently.

I also believe the physics are a little different. Looking at TheUltimateGamer95's PC run, jumping and landing seems to be quite different to PS1 in that cars don't bobble around as much on PC.

Also, models and collision are much tighter and more refined on PC, so PC can't drive 'through' a corner or a thin post, unlike PS1.

In Home Free, you can't take the hill shortcut at the spaghetti section, as the models don't let the bus get up, and also, boulders are smashed as opposed to hit across on PS1, which makes hitting them not as bad, as they're out of the way.

If I can find more examples, I will post them.