What are the long-term advantages of a US PhD compared to Europe/Oceania? I have applied to PhD programs in ecology in Europe (Germany, Denmark, UK) and Oceania (Australia/New Zealand). Now the deadlines for US programs are coming up and I am debating whether I should apply there as well. Aside from the exorbitant cost to apply to US programs I am interested in comparing the pros and cons as far as career opportunities.
I have ready a MS from a major US university and I will turn 31 soon. My career goals are to pursue a teaching/research position.

Assuming that the potential advisors satisfy my requirements (good publishing track, personable, successful students, international connections) and that there will be funding. I will consider "rest of the world" and USA.

Rest of the world:
- can be completed in three years, in this case I will have gained two years for a possible Post Doc, and also make use of my Masters
- I will be able to just focus on research without being a teaching assistant, from what I understand publications would count more than teaching assistant experience even for a 50%/50% research/teaching position
- it might be harder in case I want to find a job in the US, especially since I will not be located within the country
- there are no obligations to complete courses
- pay rate is generally decent compared to cost of living

USA:
-I am under the impression that with a PhD from a top US institution is well-regarded internationally and would be easier to find a job in Europe or Australia
- the teaching experience could be useful to me as I would like to also be involved in education alongside with research
- there is more time to explore and think about research questions and goals, as opposed to Europe where you join to develop a certain project
- the stipend and the US is very low also compared to the living costs especially on the West Coast. It would mean five years of financial sacrifice
- more chances to perhaps be involved in other projects, it seems there is more of an open research community within departments
- it might be productive to take some classes that are taught by top profile professors

Are the extra time spent and the financial sacrifice for a US PhD worthwhile for my career goals and my preparation has a successful educator/researcher? Will my international mobility be limited based on where I graduate?
I think the key question is: What do you want to do after the PhD?

There are some points that you may consider to choose a programme if you want to stay in the academia. The advantages or disadvantages of the length of these programmes depend on your training/background.


Your background. If you are familiar with the topic you are planning to work on, then you can probably start checking the relevant literature immediatly, in this case a 3 years program may be what you need. But if the topic is unfamiliar to you, then you would probably have to attend lectures and to read textbooks, in this case a 5 years program may be better.
Your CV. A work in the academia usually involves teaching and research. If you have teaching experience, then you can focus on developing your CV in terms of research. In this case I would go for a 3 years programme and get involved full-time on research. If you do not have teaching experience, then you might want to consider a 5 years PhD where you have the opportunity to teach and develop your CV in both lines.
The topic. Some research projects by their nature itself require different amounts of time to develop. For instance if you are going to work on modelling a specific data set vs. having to obtain the samples directly in the Amazon.


Regarding the mobility, I think after the PhD what really matters is your CV. Either if you graduate from Oxford or the University of Tuvalu.