They are BOTH very different cars to drive, and both have a VERY different mindset to every other car in LFS, which is why I like them, which is why I think this league is good.
The RAC is a very nimble flighty thing, which needs carefull actions on all the controls or it will bite your hands off.
The FZ5 is a huge, powerfull, heavy beast of a thing, it needs to be driven smoothly with no (or VERY limited) sliding, and lots of planning for corners, the FZ5 is fastest when it feels slow funnily enough.
Both are VERY satisfying to drive fast once you are in the right mindset, you just need to be gentle with them and show them respect.