IMHO:
Pat's "lynch pin washers":
Pro: Handy in that, by design, they can't slide on the attachment's pin and stay in the right spot between the Pat's hitch and the lynch pin.
Con: Under certain conditions, with just the right force, and the right bump, (& a waxing moon when Saturn is in retrograde, etc..) I've seen these washers "pivot" and get past the end of the lynch pin, which sends the lynch pin flying, then one side of the brush hog falls off the 3 pth. Not fun when it's an hour past sundown and you're on the side of a hill. As a precaution, I use standard washers that can't do this.
(Another solution if using the "lynch pin washers", and this is hard to explain, is if you can turn the attachment's pin so it's the hole (for the lynch pin) is horizontal, then the lynch pin is blocked from inadvertently coming out by the "bulge" of the Pat's system where it goes over the tractors lift arm)