I did not take that statement to mean that Lady Lucas was a "dimmer bulb" than Mrs B, but rather that Lady L was not any MORE clever than Mrs B. I actually think that Lady L may have been the smarter of the two, as she had her eldest daughter helping around the house, at least according to Mrs B's statements at Netherfield. Now we know that Mrs B used this in a negative way, to build up Jane to Bingley: that HER daughter did not have to be useful around the house because Mrs B hired a superior staff of servants to those employed in the Lucas household. This might be something to recommend Jane to the Bingley sisters, because they no doubt knew little or nothing about the domestic workings of their households & would look down on a woman who did. JA doesn't indicate that Mrs B's statement influenced or impressed Bingley in the slighest.