Thanks everyone.
I'm really glad with what I've accomplished, but I'm clearly a bit bitter. And i know so many students have had it worse. I'm really lucky I found a niche.
But because I spent so long floundering I've spent the last 5 months unfunded writing up. Not only that, I do have publishable content in my thesis yet there is no funding in my department to keep me and myself and supervisors know I'll certainly publish it cause it's in my benefit to do so. S1 has jumped ship (I'm in the UK and Brexit has seen mass exodus of non-British academics) and taken all his non British students/postdocs to mainland Europe.
I've got a new research job lined, in a very different field and institution (i wonder why I'm not staying!). I'm sad I'm leaving all the work that I built from the ground up, excited and terrified of moving to a different research field with limited experience.

Kikothedog, I understand projects can be handed off, but it feels like S1 is taking my IP, jumping ship and stabbing me in the back. He already neglected to acknowledge myself and a colleague as coauthors/acknowledgements in work where we fabricated the samples. One part of me wants to talk to him about this and the other wants to just walk away and be done with this experience. But this idea was what I wanted to do for my PhD in the first place!

Monika, I'll try and talk to S1. Even if I'm at different institute, I'm still the only one in my department with the most experience working with this material and understanding how it works. I'll try and put my emotions on hold.

I sometimes wonder if I've been incredibly stubborn and pigheaded to have lasted as long as I have. Not sure those are good qualities to have...
Thanks guys

If you think their research is comparable and it sounds like you'll get along with either of them. Other things then to consider is:
1) Did they let you talk to their current students? Very important!
2) What is their publication record like? Impact factors/h-index etc etc cause at the end of the day it's good (bit not the end of your career if you don't) to get at least one publication from your PhD.
3) What city would you rather live in? Do you want to be stuck on a tiny campus or have access to the "real world".
4) What lab equipment/library/resources will you have access to? Is one institution better than the other?
5) Will they let you go on conferences or study schools etc? How many will your funding allow? I got to go to one conference or school a year and I think they are invaluable experience in understanding your field and meeting other students.

A prestigious university does have its perks but if you are with a well known person in a field you like I think its more important.
Also a PhD is only an introduction to academia, your first Post-Doc can allow you to move to a place where you can develop research ideas further.
Good luck!

Hi JohnGalt,
Having gone through a mess of PhD listening to poor advice from supervisors who are not experts in the field I've carved out for myself there are a few things you can do.
1) Accept that your first document was too broad. But that it's good to get an overall view on the field you are entering. It'd be worse if it is too narrow.
2) Decide if you were to start an experiment tomorrow, what is the short term question you need to answer? What controls, equipment would you need? What is the impact of your question and once answered is it a platform for more work? This is difficult and usually a supervisor guides you through it.
3) I'd focus on supervisor 1 suggestions, if you struggle with point two. It's good to be flexible but it's bad to be dragged to far away from something you need to be passionate about for 3+ years.
4) When you feel you're confident in a direction with short term goals (with glimmers of long term ambition) arrange a meeting with your primary supervisor. Send an email or pass by his/her door and say "I've been thinking a lot about our last meeting. I'd like to talk about the PhD direction. Do you have 15 minutes for a quick chat?"
5) During this meeting say you appreciate you were broad and that this is an area you'd like to focus in. Ask about his/her thoughts and opinions. Ask about practical limitations and even if your work can link in with the wider group

If this supervisor is being helpful, great you'll feel more confident writing the literature review. If not and you really don't like the direction you're going in, talk to post docs and colleagues in the department. Ask for their advise and more importantly who they could recommend as an alternative supervisor.
It's better to have a respectful relationship with your supervisors and not worth putting up with less.
Good luck.

I'm a PhD student and writing the final chapter of my thesis. I need to Rant...

I've found myself reflecting over choices and experiences during the writing process and I can only conclude that I'm incredibly disappointed in my supervisors and academic institute. They have failed me.
I have 3 supervisors (S1,S2, S3)and only S2 (most removed from the research) has actually taken an interest. However S2 bullied my for a year, drove me into depression which forced me to start counselling and now i have a therapist. Side note S1 forgot I was his student so that was a fun conversation.
I realised for all supervisors involved my PhD was the "side project" and no one really had a clue what was going on. All the projects I was given were pointless not publishable, all the projects I came up either didn't work or they wouldn't let me pursue. I've spent my whole PhD with the attitude "I need to salvage this".
I finally found a niche, and the only reason I published two papers was because I went against what I was being told to do and actually found an interesting angle. During the process of writing both papers S1 asked "Why is this interesting again?"
The only encouragement I have had has been when I've gone to external conferences, had feed back from reviewers and an examiner during one of my PhD milestones.
Now I find out the research project I planned has been given to another student by S1 despite all the hours I spent preparing the lab reading literature and doing the background work.
A PhD shouldn't be like this. I have achieved some awesome results and physics and yet I've had zero support. This experience has diminished my passion for the culture if not the subject.
I cannot recommend a PhD at this institute to anyone.
When should a person say enough is enough, this isn't for me and just walk away?
How do we ensure we get the right support?