I've owned two 501's. Of the 5xx series, the Squire is my favorite for EDC rotation. One that I owned is long gone because I wasn't happy with loose scales and the other is at Buck Repair right now, because the blade won't stay closed. Shake and the blade rattles when closed. Turn it "up side down" and the blade falls out about 1/2 inch and it was a brand new knife.
I have delivery confirmation that Buck has had the knife for one month now ... and I haven't heard one single solitary word from Buck at all, via email or anything else. Buck repair site states that repairs this time of year could take up to 8 weeks, so without any communication, I'm just holding my breath and crossing my fingers I even get the knife back and if I do ... hopefully it works.
I've got a 55 too and even with it's diminutive size, it has one more rivet on each scale than the 5xx series. The 55 scales aren't loose nor likely ever will be. But the quality of the 55 is a whole nother story LoL and the imperfections noted (soft springs, plenty of blade play etc), have been accepted as just how Buck is these days and I knew that going in.
So yeah, Knight vs Prince? ... 501 Squire