Hi @Cotonshaded and @claraszoo! Parent of Cambridge finalist here.
In general, Cambridge colleges guarantee 3 years in college accommodation, some of which may be on their second site or third site around town or in a college owned house. There is huge variety in the cost, quality and size of the rooms and in the bathroom and kitchen provision. Some old 'sets' of rooms which are now split in to singles and may have slightly restricted privacy: one student may have to walk through another's room to access their own room.
The only way, I am afraid, is to do the leg work - college web sites, college 'Alternative' Students' Union web sites, site visits, emails to college Accommodation Officers - and build yourselves a good Excel Sheet, college by college, building by building and site by site.Two tips: the newest buildings are the best and so, overall, the newer colleges have the most consistently best rooms and facilities. Richest colleges subsidise rent and food (Hall, Buttery,cafe) and laundry the most.
But remember that nearly everyone is happy, overall, whichever college they end up at. And they have only warm memories of the friends they made wherever they stayed.
What would I do? I would actually focus only on preparation : the quality of my Application Pack and work on the Admissions Assessments. I would make an Open Application and take pot luck on Accommodation. Part of Uni life ought to be adapting, being resourceful and handling change positively. .. Just my view.
All colleges are very caring and generous where a new student has particular physical, medical or other needs. One girl actually transferred from from my daughter's college to another college after one term; she uses a crutch and desperately needed to be closer to her Department. So two colleges cooperated to make the switch happen.
Please feel free to Private Message me about rooms or anything else about Cambridge Admissions or Cambridge life.