There are a number of differences in the graduate school experience between the US and the UK. One of the most prominent differences is the amount of time it takes to get a PhD:
Time to completion:
In the US the time it takes to get a PhD in the biomedical sciences varies widely based on the program, the adviser, the student and
the research progress luck. Usually it takes anywhere form 4-7 years. In my PhD lab, most students graduated in about 5+ years. Here in the UK there is much less variability: it takes either 3 or 4 years; and you know how long it will take from the beginning. This is because most PhD positions are offered as studentships that are funded from a specific grant for a specific period of time to perform a (usually) well defined project. Once your time is up, well you better be done because there may not be any cash around to support you!
There are some obvious advantages to having a set time limit on the PhD experience (although I think 3 years is too short; I’ve been told there is been a trend towards having more PhDs take 4 years…). Having a clear deadline for when funding runs out may help keep a student focused on making brisk progress. It is not entirely uncommon in the US to find graduate students that sort of meander about and don’t get their ass in gear until 2-3 years in. Having a set time limit also cuts down on the potential for advisers to abuse graduate students by forcing them to stick around longer than necessary to continue to work on a project.
However, I also think there are some significant drawbacks to this approach.
The primary one is that students don’t come out as with as much professional experience as I think is more typical in US programs. Given the amount of time it takes to really get going in a lab and get a handle on the literature in the particular sub-specialty, there is limited opportunity for giving talks or multiple poster presentations. In addition, I also think graduates from UK programs are less likely to publish as much or have as much opportunity to generate multiple first author publications or apply for their own support. Given the time constraints, they also appear to be less likely to have the opportunity to dabble or go after more high risk or exploratory research if they are only working on a small piece of a much larger project, as the cost of failure is much higher when the time frame is more limited.
Thus, at the end of the day, I think a student is likely to be more competitive overall and have more professional experience/knowledge about the scientific process with respect to publishing and grants after graduating from your “average” PhD program in the US than the UK. Given the 1-3 more years it typically takes to get a PhD in the US, there is significantly more opportunity to develop a CV. However, if one were to control for the total number of years being in science, I think many of the differences may very well vanish as I don’t believe there are any significant differences in overall quality of the PhD programs between the two countries.