You are wrong. They both have "3D" trees, well a mixture of 2D and 3D trees based of distance from camera. Both have 3D stems, but the leaves are 2D. in Forza they use the classic billboard technique, a bunch of 2D flat textures arranged to give the illusion of depth and 3D but if you look at it from a certain angle the illusion fails you can see all the flat 2D textures. GT7 uses 2D forward facing sprite which always orient themselves to face the camera. If you are driving fast, you won't notice but if you move the camera slowly you notice the sprite orient themselves to the camera. The difference is in GT7 leaves react to lighting while Forza does not.
Forza
Closer look, you can see the flat leaves.
GT7
Which you prefer is up to you but both games use a mixture of 2D and 3D trees.
This is demonstrably false. Like has been shown by the comparison. Some things are better and worse in both games.
Yes, there is clearly room to argue here like above. They both use 2D leaf textures but differently. One is a billboard while the other is self-orienting sprite. One simulates light passing through the leaf while the other does not.
Depends on what you mean.
In replay mode? Yes, you can absolutely say that as GT7 RT in replay mode is more advanced than what you see in FM8 in the replay mode.
In gameplay RT reflection is very limited to car reflecting cars and at a very limited range and yes that is better than GT7 car on car reflection
FM8 also uses screen space reflection and cube map for everything else at 30fps while in GT7 screen space reflection run at 60fps except for cockpit view which runs at 30fps as well as cube map.
It's so easy to say RT better than no RT but how its applied matters.
I honestly don't think you know what you are talking about here. There is no evidence of light bouncing or indirect lighting of track and trees. A bounced light picks up the color of the object it is bouncing from and illuminates the surrounding i've not seen a single material that shows or says that.
I find majority of people arguing in this thread are doing so without any technical understanding of what they are arguing about. There is nothing wrong in preferring one over another but to say one is better with so much certainty yet being entirely wrong like claiming Forza has 3D trees while GT7 doesn't is entirely wrong.