Rankings are not really that useful, as my American flat mate says "Ignore rankings, they are just rate universities who spend the most money buying off assessors." I do not think that is quite the same in the UK, but it is worth remembering. For example, I can show this ranking
http://www.timeshighereducation.co.uk/world-university-rankings/2014-15/subject-ranking/subject/arts-and-humanities, which puts Edinburgh way above St. Andrews. It is not that useful though in reality other than for Wikipedia pages. Both Edinburgh and St. Andrews will have top English faculties so academically the difference will be very limited. You can look at the courses on offer, but academically it will only be the courses that are the key difference. As I have written above, I think Edinburgh easily wins as place/student city. My advice would be if you pick Edinburgh to make sure you do not to English
and Scottish literature, reading-wise that is a known suicidal combination.
The faculty is among the best at Edinburgh it has a cool building in the Old Medical School, just next to Teviot (the SU) and has a wide variety of academics within in. If you look at the recent research assessment you will notice the size of Edinburgh's contribution for assessment, which shows how big the faculty is. Consequently there is a wide variety of courses on offer from all areas of world history, as well as the fact you can take outside courses in sub-honours. Marks are generally fair, but feedback kind of depends on each tutor. You can always arrange a meeting/go to your tutors office hours to get detailed feedback, although only some/few will organise this themselves. However really I have found if you are genuinely serious about your subject you will know that you need to spend 30 hours (which is recommended) on an essay to guarantee a solid 2:1, and no amount of detailed feedback will necessarily help you in achieve that.
In first year I had around six essays a semester, but this year it has gone down to around four. Tutorial work depends on tutor. Last year in British History I had a tutor who made us do 100 pages of reading and 800 words for every week. That was hell, but he was the best tutor I have had. Mostly you just need to have read a couple of articles and some primary resources. Some tutors have essay guidance sessions, especially in first year. These are fairly handy, although I am of the belief that the best historians will have a fairly good understanding coming to university what constitutes a decent essay anyway. Your courses tutor normally marks your essays so it is definitely worth asking what they specifically like in essays, even if they do not bring it up themselves. It is quite easy to pass without doing much work, but to get 70+ average is hard for anyone. There's a bigger jump between 67-71 than from 0-65. To get a decent year abroad if you want to do that then you need 65+ average in first year. I managed 68 and I partied pretty hard, although spent a lot of time in the library as well. Work hard-play hard is definitely a thing you learn.
I would advise Pollock. While the idea of your own kitchen is nice, it actually saves a lot of thought having catered, especially settling in. Halls in Pollock have their own pantries on every floor anyway with a microwave etc., although no ovens. You will have your own kitchen when you move out of halls anyway for three years so you are not missing out on anything. Kitchens shared between 8+ people are also famously (and as I can testify from those I have seen) dirty, which is something you will not have to deal with. Although allocation is basically random within Pollock, Chancellors and Turner/Lee/Baird/Grant are probably best. I was in John Burnett, which is very hotel-esque, although it is the home of the true social élite of Edinburgh University.
So far for me it has been the most interesting part of my life. 2014 was probably the best year of my life so far, and I am off to California next year to that will be an excellent adventure. There's a diverse student body from varying social and economic backgrounds, including a large international student population, so I have met people unlike any I had previously, which has been great. My degree is very flexible with no compulsory courses, so I have a lot of academic freedom too which has been nice. Booze is relatively expensive (by English standards, St. Andrews is the same), but abundant, once you get used to the fact it cannot be bought at Tesco in Scotland past 10pm. While there may not be so much culture as in London, Edinburgh is a capital city of sorts, which means there is enough to keep you ticking over, Glasgow is 50 minutes (£8) by train away so there a plenty of big gigs there too. Societies can be/seem a bit cliquey at first, but you get past that quite quickly. I think that has covered most of it, hope this has helped. Maybe see you when I come back next year!