i actually haven't been to a single open day and my main reason why i want to go to trinity hall is because I noticed its position has improved substantially recently on the Tompkins table, which suggest that it is doing a good job of making their applicants perform better
fitz because it has cheap wifi and the pros and cons page doesn't really list much bad stuff about it and I suspect applying there would increase chances of getting in to cambridge (admissions tutor reported a fairly low UMS average for maths, like low 90% ish I think? unlike christ which has 97%)