1) Agree
2) Partially agree - I haven't gone to the length of writing anything down but I have been modelling it in my head for weeks. As you say later in your post a lot of it is intangible hence the difficulty in deciding.
House/Apartment - I currently stay in Yorkshire so housing is cheap. As a contractor my Ltd Co can pay my rent as a valid business expense. Switching to permanent employment would mean that I have to pay this out of my personal income, so in that sense the costs would go up and not insignificantly so.
The job security is a strange one - I contract for a large consultancy with work for a large Government department. The work won't dry up anytime soon and when it does, my specific skill set would allow me to find more work (either abroad or in London). People I work alongside are being offered year long renewals - practically unheard of as far as I am aware.
The "startup" is a Government funded organisation so although a permanent position, there is always the chance the funding will dry up.
The hours should in theory be a similar 37-40 hours per week. Whilst sometimes in my current position I will work a 12 hour day to help with deployments or live issues, it is rare. The client is very flexible with regards to office hours. I imagine the new role would be similar, however there is a risk that it ends up being worse with longer and less flexible hours. The job posting specifically lists working from home as a perk so I suspect it's fairly progressive.
Friends is a big one - Yes I have made friends with people on the current job and I will miss them sorely, however I also have friends in Manchester which is within commuting distance of the next job. I would be looking to cultivate old friendships at the expense of newer ones. The Christmas journey home would be an hour less on the motorway so not a huge factor although would mean frequent visits are easier.
The million pound question is the retirement part. Whilst I don't think I will be ready to completely stop working in ~10 years, having the option to sounds very appealing. I would like to be free to spend time with my (imaginary) family and have the creative energy to work on other projects without worrying about financial viability.
Ultimately the tradeoff probably comes down to on the one hand having a job I can be proud of (I am working on a cure for X) that will also be incredibly stimulating intellectually, versus the surety of the job I have for now, with the contractor income that allows me to become financially independent a lot sooner.