There is a reason for the breakdown of the units of comparison, which would result in using the particular comparable or comparables more similar to the subject in gba, rooms, units and bedrooms.
A discussion in a two unit report I looked at this week:
There are basically four units of comparison available for estimating the market value of small residential income properties in the sales comparison approach. These are the price per square foot, the price per unit, price per bedroom, and the price per room indicators of value. The units of comparison analysis are limited to the closed sales with the one active listing reflecting the upper end of the range.
The price per square foot indicators of the closed comparables range from approximately $516 to $690 per square foot. Typically larger units have lower price per square foot indicators than smaller properties. A price per square foot indicator of $550 is considered to be appropriate for the subject given its smaller size relative to the comparables. This is within the range indicated by the comparables.
2,070 Sq. Ft. X $550 = $1,138,500
The price per unit indicators of the closed comparables (all similar two unit properties) range from $508,500 to $636,500 per unit. Typically, price per unit indicators are higher on properties with fewer units then they are on properties with more units. All of the comparable sales have two rental units in this case. A price per unit at the middle of the range at $550,000 per unit is considered appropriate for the subject due to its physical characteristics and overall market appeal. Based on the price per unit indicator, the estimated market value of the subject property is:
2 Units X $550,000 = $1,100,000
The price per bedroom indicators of the closed sales range from $254,250 to $279,000, however all of the comparables have fewer bedrooms than the subject, warranting the use of a lower price per bedroom indicator. At $200,000 per bedroom:
6 X $200,000 = $1,200,000.
The price per room indicators of the closed comparables range from $127,125 to $141,444 per room. Typically, properties with a greater number of total rooms reflect lower price per room indicators than properties with a smaller number of rooms. The per room indicator considered appropriate for the subject is $120,000 per room, below the range of the comparables as the subject has more room than all of the comparables. Based on the price per room indicator, the estimated market value of the subject property is:
10 rooms X $120,000 = $1,200,000