Just start with a few basics – that will cut things down considerably. Your search for the secret/unknown factors that make the big difference is somewhat pointless.
As you get further into the process, you can add or refine things as you discover the things that your kid does/does not care about.
The biggest sorting factors in the process are the obvious ones: (i) what school can my kid get into, (ii) what school can I afford to pay for and (iii) what kind of school does my kid want? The list gets short very fast once you’ve identified that you are looking for, as an example, a top 50 private school, midsized, with an engineering program, not rural, not in a cold place, not a big greek school, and where my kid could score some merit aid.
My kid’s spreadsheet started off with:
USNWR ranking
size (undergrad enrollment)
m/f ratio
location (urban, suburban, college town, rural) and also region/weather
50% SAT range
50% ACT range
Standardized test writing section required?
SAT subject tests required?
Admission plans (EA, ED, ED2, REA, SCEA) and applicable dates
overall acceptance rate
ED acceptance rate (if applicable)
% of seats filled via ED
Sticker price
Availability of merit aid (if that’s important to you)
Does school meet full need (if that’s applicable to you)
% of kids in greek life
Relevant majors offered
blank column for comments
Spend the $10 bucks to get the magazine version of the USNWR rankings when it comes out in September. The 2 page ranking tables they have in that magazine are pretty much a basic starter spreadsheet. You might even be able to download those tables into a spreadsheet.