Have you used it and do you have real problems with those VNA or do you want just to talk about a theory of VNA design?
(I have LiteVNA64 just about three months and found it extra-usefull, especially for it's price. I have done a lot of work with it, a lot of R&D where you need VNA, and I have to say that for 100% I don't care which wavefom it uses if it does its work).