IN MY MARKET, we have numerous neighborhoods that consist of more than one subdivision. My brother, an SRA, has used the grade school as a search feature. He believes this is the one common factor that really defines the "neighborhood". Another well qualified appraiser and AQB certified USPAP instructor likes to draw the search area using the "polygon" mapping feature available on our MLS.
I have used both plus those defining things such as neighborhood name, subdivision name, or MLS marketing area identifier depending on the nature of the ..."neighborhood". Still conflicted about the selection of "comparable properties". My thoughts are the data, if available, for the grid portion of the 1004mc should be those properties a buyer for the subject property would consider when selecting a property to purchase.
Many years of sales experience as a real estate broker, managing broker, and real estate sales trainer covering 6 western states has convenienced me most buyers are pretty much style specific and also are driven by number of bedrooms, baths, location, and school districts. That is not to say buyers will not mix split levels (tri-level and four-level) in with a two story. But those wanting a ranch style are not nearly as flexible in their choices. The condo market is entirely a sub market and doesn't compete well with fee simple.
One thing I do know, the form was poorly thought out. It is way too inconsistent and often lacks sufficient number of sales data to be meaningful. The additional research required IN MY MARKET typically means an additional 30 to 60 minutes and that includes filling out the form. One good thing it does do is affording me the opportunity to take a better look at what is occurring such as LP/SP ratios, days on the market, and supply and demand factors. In most sub markets, ie., IN MY MARKET things have started to improve considerably. Of course we were never as hard hit as other markets primarily due to the heavy military influence here. Our number of foreclosures is and has been lower than the national average. Same is true for unemployment.