The way TC operates is when it sense that a wheel is slipping or spinning faster than the other one, it will pull power from the wheels to allow it to catch. This means that full engine power is not transfered to the wheels at all times.
When it comes in there is a short lag until full power is restored to make sure you do not slip again so it will slow you down.
If you want to go fast in a straight line then yes, go ahead and turn it off and it may improve your times.
