I really like the color version. I think the redness of the roof complements the green of the grass. The polarizer has really brought out the dark blue of the sky which blends nicely with the lighter blue on the walls. B&W work best when you have tonal contrast which really brings out texture, lines, and patterns without the "distraction" of color. Do you think there is more contrast brought out by the color version than the contrasts in the B&W? Is there more contrast when the wall is in color than the B&W version?
Maybe the answer lies in what you wanted us to see? Why did you take the image? Why do old buildings have so much attraction? Old barns, sheds and crumbling walls make compelling images. What emotion did you want us to have here? Sometimes I cannot answer such questions in my own images, so I am not trying to be flippant. Which version do you think best portrays your reasoning? Sometimes I am drawn to a subject because of color, so I rule out the B&W.
BTW Check out OnOne Software Perfect Suite 7, B&W. It really has effective ways of post-editing with individual color in B&W conversions. For example it would allow you to darken or lighten the green grass without effecting the rest of the image.
PS Looking at both images again, the black section of the building in the left corner bothers me less in the B&W image, maybe because it goes better with the blackness of the sky than the blue of the sky with the color version. (Ansel Adams included a lot of black spaces in his images)