I am limited by the size of the space where I must place my TV. The 40" Samsung TV is a much better fit than the 43" Sony4K UHD TV, but I read that the Samsung's motion display characteristics were poorer than that of the Sony. If we only watch news, baseball, movies and videos of our grandchild will there be a significant problem with purchasing the 40" Samsung 4K UHD?
Sony doesn't make panels (and motion blur is a characteristic of the panel). They used to buy their panels from Samsung, but I dunno if they still do. However, even Samsung does not use exclusively Samsung panels. They buy some of their panels from AUO and Sharp.
It's really difficult to comparison shop based on generalizations of reviews of a manufacturer's TVs. You need to compare reviews of the exact models you're looking at.
Edit: Also worth noting that in the review I linked, even though the Samsung panel had worse response time than the other two panels, the motion blur on it looked better than the other two panels. It's hard to boil down your eye and brain's perception of motion into a single number like response time that's easy to compare.