Alec KI have not seen either, but just in case no one else offers an opinion: Considering that the Williams Brothers kit dates from 1974, I would venture a guess that the Azur-Frrom kit is superior in every way (details, fit etc.). Most builders would probably consider the Williams Bros kit a nostalgia build. There are two review available for the Azur-Frrom kit in case you have not seen those:
ipmsdeutschland.de/F..Export_WH-2_WAA.html
britmodeller.com/for..0042-172-azur-frrom/2 March 2021, 02:22