I don't have any experience with RM Williams but here's my two cents:
1. The RM Williams boots do not have a stitched seam below the elastic band on the side. I assume this makes the lasting a bit more difficult and hence is rarer - I only see it on G&G.
2. The Church Beijing is part of the City Line which uses lower quality material than that used in their Custom Grade line.
3. If you decide to buy the Church Beijing, other online retailers offer a lower...