v1.2 is better for speeds (still not 100% by my testing, but pretty damn close! (2.4, 7 & 16). However, adjusting stuff in TDU is a nightmare! Changing one parameter can affect both straight line performance and handling. For instance, Downforce and Grip both affect acceleration and cornering. I have spent MANY hours tuning TDU cars and have basically come to the conclusion that replicating all aspects of real-world performance is not possible, there will always be a trade off between straight line and cornering performance and because there are SO MANY variables in the equation it can drive you ABSOLUTELY NUTS trying to juggle them all to make everything work!
So as I mentioned earlier, I tend to get my 0-100 time & top speed perfect and forget the other times, it's just too hard and parameters you adjust can massively impact handling.
Hopefully one day physics engines are a perfect simulation of reality and you just need to plug in the real world numbers and it all works first time. In the mean-time, we can only dream :)