Wedi vs Delta Boards

[One Day]

Kerdi has waterproof core and waterproof fleece coating, wedi just has waterproof core and cement coating

Wedi's cement face is better than some of the cheaper ones though.
Unless the application is commercial, i.e. in use 24/7/365 the boards are all much of a muchness.
Incidentally, Kerdi isn't classed as vapour proof (yet) without Kerdi DS membrane over the top.
Wedi isn't either without treatment, but in both cases for normal domestic use, they might as well be.

 

[Flintstone]

I’ve used some insulation boards that have been poor quality, with a fibreglass type of grid was peeling off, unevenly coated etc.