Well...the one-story plan (without the basement and bonus room) is several hundred square feet larger than the two story plan, I believe.

Neither plan will be particularly cheap to build with their notch-os and bump-os (architectural terms), and complicated roof framing.

The one-story has much greater foundation, first floor interior flooring (assuming all first floor may be higher grade finishes than any second floor finishes), and much greater roof structure. Plumbing lines, waste lines and HVAC supply/return ducts will normally be greater. The overall plan is sprawling, disconnected with absolutely no efficiencies anywhere.

The second-story has a very expensive wrap around porch on front, plus rear porches). The plan is comparatively more efficient and compact, with only a small usable second floor.

If money is an object, the second floor design may be somewhat more economical.

thanks Virgil! My assumptions included increasing the size of the 2 story to make it the same sq footage as the 1 story. the sq footage would be added to the back side of the house in order to eliminate the rear porches on the 2 story.

Won't you still need rear porches, decks or the equivalent for indoor-outdoor access and activities? Can't imagine a house, especially with the family/living room on the rear without outdoor access...!

the one story will be significantly more expensive with foundation and roof alone. building "up" is almost always cheaper than building "out".