If I have to pick I would prefer concept B, but to be honest I find both concepts to look quite dated.
Focussing on just the header and navigation of concept B:
By giving this design room to breathe and a stylish type that matches the purpose of the site, I think things will improve a lot.
I should add that design C is a non-starter as far as the client is concerned. But I would be interested to hear what you think.
It looks like your client is quite conservative, up to the point where it is becoming counter productive. Anyways, since your client will not go for C I will make this quick:
In general it looks better, the header image explains better what the site is about although it is quite huge. Nice touch on repeating that image outside the page flow
Allmost all gradients in the design are not very subtle, they should be toned down a little with less contrast.
The white text on a light grey background for navigation is not legible enough
The navigation links are quite huge. I still don't like the font, sizing and boxes used.
As mentioned earlier, the text below the navigation is not that useful to a user I think.
I hope I do not come across as too critical. I understand it is hard for you if you are severely restricted in your design freedom.
Thanks for the additional comments. Although I can't use the design your criticisms will definitely help with future projects.
The issue of font choice is somewhat subjective and I have to stick to fonts already associated with the client's brand identity.
The only thing I would comment on is the issue of the navigation size. The buttons are quite large (not as large as design B though), but this was intended to make them user friendly on mobile devices etc.
...but glass enthusiasts will be fine with it so long as it works right.
Thanks for the comments.
I agree about the dated comment but I have been restricted by the client's direction.
I agree with the rest of your comments, but thought that design A addressed many of these concerns.
I did have another design in mind but it was rejected by the client. As another option, perhaps you could comment on design 'C' - now attached.