I love mine on a 1894 SS 44 mag, but there is one downside. The Lyman is easy to make precise adjustments with, the Williams is not. You have to loosen two screws and guess the amount of adjustment, with the Lyman there is a well-calibrated scale. But once it's set, you're done!
If the $15.00 price difference doesn't bother you, I'd get the Lyman. If you're going to sight it in once and leave it alone forever after, the Williams is clearly the better buy. HTH.
PJ