Wiliiams wrenches are strong performers but, are not the same as Snap on. To begin with, the full polished Supercombo wrenches have a beam that is more rounded and twice as thick as a similiar sized Snap on combination wrench. This can be handy for people with bad hands or that don't like the knife edge feel of some wrenches. However, with the thicker beam, comes increased weight and a different sense of balance and feel. The teeth on the Supercombo aren't as aggressive as Snap on's flank drive plus. Williams is more like the notched end on Matco's optitorque or Mac's knuckle saver. The area behind the base of the open end on a Supercombo wrench is machined down to be thinner than the rest of the wrench possibly for improved access or who knows?, ask williams.
Williams tools need to be judged on their own merits. Don't think you're buying a Snap on tool with a Williams name on it. Although many Blue Point Tools are a perfect match for Williams. Let's address price for a moment. You can get a Snap on flank drive Plus metric combination wrench set in sizes 10-19mm for $320 and change off of the truck, or You can get a Williams fully polished Supercombo set in the same sizes for $98.61 depending on where you shop. They are NOT the same wrench though. Don't be like those idiots on Ebay that think that just because a brand is a part of the Snap on tool dynasty,(williams, Bahco, CDI, Blue Point) it's a Snap on tool. It's a Snap on tool if it has Snap on on it.

The pictures compare a 15mm snap on fd+ with a Supercombo 15mm.