I like A. The name, Architectural Set, stands out right away. The lines make me think something is designed and built. The blurb in the bottom right corner is helpful in explaining the attributes. But I don't think you need "decorate" in the subhead.

Second choice is B. I just didn't pick that one as first choice because the title gets lost as it is placed vertically on the left side. Other wise it is quite nice. I like "cardboard + connectors + imagination".