I would sell the CV and keep the Summicron based on intrinsic market value, but you may find that it won't fetch much anyway so is it worth selling?

On the other hand the 40mm CV has a character, both in physical size and rendering, very similar to the Canadian made 35mm Summilux, soft and glowing wide open, sharpening up and becoming a lot more conventional stopped down. OK it may not have the fine bokeh of the Summilux, but it isn't far off. The other thing about the 40mm focal length is that it fits most of the Leica 35mm framelines more tightly, slightly inside the frame or dead on the frameline instead of slightly outside (at average medium to distant focusing distances). Some people find this easier to visualise and deal with when quickly composing the image than imagining how much lies beyond the frame.