Actually it's the other way around
LTC-R for mod, Speed 6 for spec. Barry Baker tried it first and it worked great for him, I gave it a shot and had the same results.
The LTC-R just goes into the corners a lot harder and allows the car to roll more which in my case really frees it up in the hairpins. The Speed 6 stays flatter which keeps the car a bit more planted, but the body itself seems to have more rotation.