In terms of handwork both are excellent with Bn you can ask for optional extra handwork. Both have excellent fit as you would expect for bespoke. I like the styling better on my Bn stuff, they do the spalls camicia better than WW Chan.
The guys at Bn are young and very motivated and often travels to Italy to learn more on how to better their craft. Price wise both houses are very similar.
I have gotten great service from both houses but as I mentioned above there have been changes at WW Chan, their reluctance to except CMT is a big minus for me, one of the reason I started to look for a alternate tailor. Two fitting are schedule with your appointment while in the old days there was no restrictions on fittings. If you ask them to make something that is not within their house style they may very well refuse you. I find Bn more flexible in that regard.
I will continued to use WW Chan but I must admit I am really happy working with Bn and I can see majority of my commissions will be coming from them in the future.