In addition to differences in the time it typically takes to complete a PhD in the US and UK (as discussed here) there also appear to be some important differences with respect to funding. In many cases (although not all) when you apply to obtain a PhD in the UK you actually apply to do a “studentship” with a specific PI. In other words, a PI gets a grant that includes funding for a PhD student, and they then advertise that they have a position available for which they conduct interviews. The department only seems to be tangentially involved. It seems to be much more like applying for a job than applying to PhD programs in the US where you typically apply to a department and also perhaps to work with a specific PI.
This being said, there is some variability here depending on where funding comes from. From what I’ve heard there are some places in the UK that may offer support via the department or institution. However, I suspect this is more the exception than the rule (please do leave a comment if you know otherwise! These posts seem to be the most popular of mine thus far and I’m sure there are numerous future PhD students that would appreciate as much insight as possible). In the US there seems to be a lot more potential for departmental support, particularly given that graduate students are usually requested to be teaching and/or research assistants whilst in graduate school in return for support.
There are two significant drawbacks that I can see for the UK PhD funding system as I understand it: 1) Because funding is typically tied so tightly to an individual investigator, it appears almost impossible to switch labs at some point during the PhD program. If your funding comes from either a self-obtained grant/fellowship or the department, you may have more flexibility in case you find yourself in a bad situation. 2) You may not get paid a stipend whilst you are writing up your dissertation/thesis/viva in the UK. In many cases the PIs request/require that you work in the lab until funding runs out, but this gives you scant time to do all the necessary writing. Thus, you may very well spend several months living off savings or working another
menial job to support yourself while you finish your writing. While this does not always appear to be the case, it’s worth having a conversation with your PI and/or other members of the lab about this before embarking on a PhD. Needless to say, I find this practice to be extraordinarily unfair to the student.
With respect to graduate student support in the US, I think the biggest concern is that a considerable amount of time can be taken from classes/research by being a teaching and/or research assistant. This can significantly hamper progress towards getting up and running in a lab, particularly right at the beginning of the program and can significantly increase the time it takes to get the PhD. Other than that, knowing that there may be multiple sources of support can lend some marginal sense of security that is otherwise lacking in the
rat race quest for enlightenment that is the pursuit of a PhD.
As far as the amount of compensation is concerned, it appears to be fairly equal in the US and UK. Your stipend is likely to be paltry either way. The biggest issue with compensation in the UK is if you are doing your PhD in London. London is a very expensive city, and although most schools appear to offer a sort of “London allowance” it is probably quite difficult to live comfortably on the stipend alone.
For anyone considering embarking on the road to a PhD at a particular institution or with a PI, the best advice I can offer is ASK A LOT OF QUESTIONS. Particularly about the pragmatic details as there is a lot of variability out there. You want to remove the blinders of undergraduate ignorance as best you can and delve into the real world of research with your eyes wide open.