Currently have a Drayton Wiser system with a very old boiler which I intend to have replaced in the near future. Thinking of having a Vaillant ecoTec plus regular boiler which is not Opentherm compatible without the addition of VR33 PCB which would invalidate the Warranty however I like the idea of being able to have a 10 year Warranty. Property is a detached 1970's property with 2 heating zones (15 radiators) and bathroom heating on the primary circuit of the hot water cylinder.

Is Opentherm so much more efficient that I should consider a different boiler?

I appreciate that this is not really an automated home question but you guys seem to have a real expertise.