After hearing the white based KR 5U4G, and owning the EML 274, I think the Chatham is quite a bit better than either.
Whilst KR and EML make some excellent triodes, I'm not really convinced by their rectifiers so far. I was going to order the KR RK recti, but not now.
I have to disagree with you regarding the KR 5u4g white base anniversary rectifier.
As good as the Chatham potatoe masher is (and especially for the price), the KR 5u4g white base anniversary recti is (for me in my GG at least) still a considerable bit better sounding than the Chatham in every category.
When comparing the Chatham to the EML 274b mesh, I would say it depends on the system. The EML 274b with its airy high range can add some sparkle in a darkish system, whereas the Chatham is more balanced than the EML, it is rather a little on the robust side tonally.
For me, it is nice to have the Chatham but I would always want to have the KR 5u4g white base or maybe even the RK 5u4g (that I unfortunately haven't heard yet. Same is fact for the Takatsuki 274b).