Use a Pugh Matrix.

I use these for real estate, because houses can be so variable and impossible to compare, and one needs a tool that measures each house's CTQ's on a level playing field.

1. First you define your list of CTQ's (Critical to Quality). These define what is important to YOU.
2. Then you assign a weighting factor to each CTQ. Say 1,2,3,4 or 5.

Steps 1. & 2. will consume the majority of your time.......

3. Now you evaluate each unit by giving a score for each CTQ. I use 1, 3, 9
............ 1 = less than I expected; 3 = what I expected; and 9 = significantly better than what I expected.

When you look at each house you will focus only on YOUR list of CTQ's. Sometimes you have to rebuild your list of CTQ's to get your goal(s) correctly defined.

You wind up with "Score = Sum of {CTQ W.F.} times {score for CTQ.}

To wit:

1. 3 x 3 = 9
2. 1 x 4 = 4
3. 9 x 2 = 18
Score = 31

Some CTQ's for houses:

1. Traffic Pattern (how do people move through the house?)
2. Quality of Construction
3. Landscaping
4. Location - w/r/t Work
5. Location - w/r/t Schools
6. Location - w/r/t is it on a busy street/road?
7. Basement (Dry?)
8. Storage
............. and so forth.

At this point, comparisons become easy.

You can calculate

COST = "Price / Score", and "Price / Square Feet"

QUALITY of Sq. Ft. = "Score / Square feet"