That's a great question. Price per square foot can be misleading, but can certainly give a good barometer of price ranges. It will not account for many design features and unique items for a give home. When you are buying using the Cost Value Approach (i.e. price per square foot) can be a great negotiating strategy. Sellers will negotiate from a Market Value approach. These two different perspectives of value will not always reconcile but often times buyer and seller find a happy medium.
NO, value is measured not only by price per square foot but by condition and then amenoties or upgrades such as a finished basement, garage, fireplace, hardwood floors, ceramic tile, whirlpool tubs and such. The best way to compare is to assess what the value of each is in todays market given all those factors.