Cambridge is tiny. They are all about 500 metres apart. I could throw a ball from Trinity Hall and hit King's and from St John's to Christ's is a 5 minute walk through the centre of town.
They are all based on traditional architecture.
You've got to love tourists to enjoy any of those 4, because they are infested with them.
Old Colleges tend to have far fewer en-suites than newer Colleges, you can't retro-fit en-suites in listed (generally pre1850) buildings, so living in old buildings and having en-suites is very rare. Besides, accommodation is organised by student ballot, so you only get 2 years of your choice.
Choosing a College by whether it has Fellows in your subject is rather like choosing to live with your Head Teacher for 3 years. It suits some people, but consider whether you really want to live in the same space as your academic markers. When you've got a late paper to submit and you've hung one on the might before, you really don't wnat ot meet your Tutor in breakfast!
Choosing the College with your favourite scarf colours is as valid as most other measures.