The 1800X is the highest binned chip out of the Ryzen 7 lineup, followed by the 1700X, and the 1700.
While you might get lucky with a 1700 and be able to overclock it as high as the average 1800X, in most cases, they'll overclock worse, or need higher voltages to reach the same clocks. However, keep in mind that most, if not, all 1800X and 1700X models don't come with a stock cooler. The 1700 does.
So if you want whatever clocks you'll be able to achieve and have a stock cooler, go for the 1700. Otherwise, go with either the 1700X or the 1800X depending on your budget.