In more cases than not, the AWD version has faster ET's vs the RWD version but at a slight slower trap speed.
However, where wheel spin isn't much of an issue, the RWD will be the faster car.
I highly doubt the ST will have much traction issues especially at the weight it is in stock form. The F-150 4x2 was about .3 seconds faster trapping 1-2 MPH vs 4x4, I expect the RWD ST to have similar results vs the AWD.