Mean What You Say

Here is a recent conversation my son and I had while perusing the Lego aisle of a store. I'm learning that I've got to be prepared to defend my position- even if I think it supports his.

My Son: "Mom, isn't Lego Set A better than Lego Set B?"
Me: "They're both pretty cool."
My Son: "Yea, but isn't Lego Set A better than Lego Set B?"
Me: "Yea."
My Son: "Why?"
Me: "Well.... Lego Set A has X,Y,and Z"
My Son: "Yea, but Lego Set B has this, that, and the other."
Me: [Foiled again]