I got a question about which degree would make you more employable the other day, and it made me think of a new angle to compare the two systems. Usually, when I think about the 2 systems, I just think what kind of job would I get at the end of 3 yrs (UK) vs 6 yrs (US). However, a more equitable comparison would be 3 yrs UK + 3 yrs teaching in comparison to 6 yrs US. In those terms, even if you end up teaching at a lower than desired university for your first 3 years, that experience gives you two advantages: 1) good teaching experience to enhance your CV and 2) 3 years of full time pay, so that when you are at the end of the 6 yrs, you would definitely be in an equivalent position of a 6 yr program if not better. Obviously, these aren’t the only factors, but it does shine a different light on things.
Note: I hear the top tier US universities and UK universities have roughly similar in-program teaching opportunities as preceptors (US) or seminar leaders (UK). For each, someone else lectures and the phd student leads seminars focusing on group discussion throughout the term. With a longer program one gets more experience doing that in the US, but on the whole the experience isn’t substantively different. At the same time, full lecturing opportunities may come along in either system. E.g., here in Durham people periodically get full course teaching opportunities with St. John’s college in their ministerial training programme.