Talking to european grad students, it appears they have lives during grad school. People talk about it like a job with fixed hours. The average systems PhD student at a top US or Canadian school lives in the lab.
Show me European PhD students (current, or recently graduated) who have a publication list as impressive as http://web.mit.edu/ralucap/www/#Publications or http://www.cs.berkeley.edu/~jduchi/ or http://research.microsoft.com/en-us/people/parno/parno-cv.pd... (counting only papers 2010 and before)
This is a best vs best test (as opposed to an average vs average test which requires more painful empirical effort), so focus on the top European PhD students. If you have methodological issues with a best vs best test because it doesn't not reflect the average PhD experience, let me know as I cannot think of any realistic reasons why it would be a bad test.
The idea is that the top grad student shouldn't be above a certain threshold, because if they are, they should have a Ph.D., not be artificially held back.
We now have to jump through a lot of hoops - 9 month, 12 month, 18 month review panels. It's a pain, but it's obvious they're trying to make sure you don't spend a year in write-up mode. They absolutely want you through the system, because if you don't finish on time, the department gets a funding cut.
And actually you make a good point. In the UK, PhD students are fairly well paid. I'm on a CASE program and make around £17k a year tax free (outside London). The nominal wage is £13.5k for outside London (£15.5 inside). We're treated like research staff and not cheap labour.
I'm sure it makes sense in the context of European academia, which illuminates the contrast with the US.
You cannot judge people on long lists of conferences. The people you cited have enviable CVs but only three or four peer reviwed journal papers (prior to 2010) between them. This is comparable to anyone in the EU. What are the impact factors of those journals? I have no idea and am unqualified to judge. It depends entirely on your field and what the big places to publish are. For me, an imaging PhD student, it usually starts with ICCV and CVPR (and of course SIGGRAPH), however the actual citations come from journals, not the conference papers.
I have been chastised by my supervisor for citing proceedings before - a lot of people don't consider them peer reviewed and that makes a big difference.
I know people who got papers in Nature or Science during their PhD posts. In astrophysics, people regularly get four-five peer-reviwed papers over the course of a PhD because it's a publication-heavy area. A single Nature or Phys Rev citation is worth a lot more than five conferences you attended. I probably won't publish more than a couple of papers in my field, but I'm not expected to as some of it is commercially sensitive (though I may get a patent out of it instead - and more importantly, a job!).
At the end of the day, does it matter? Very few PhD students are genuinely top tier. Most of us are happy making a dent in our little niche and will probably get comfortable jobs afterwards. Unfortunately things inevitably become a slanging match :(
But in Europe, it's more similar to the way it is in other fields in the US, such as physics: conferences are considered a fine place to present small bits of work, or work in progress, but not a proper archival publication for major results, which should go in journals. Journal articles get the main prestige and are what's expected on a CV, and citations to journals are strongly preferred over citations to proceedings.
This leads to an interesting situation where some prominent tenured professors in the U.S. would be weak candidates for European faculty positions, and vice versa.
I did get the impression that people tended to republish really 'big' results in places like IJCV or TPAMI. But, coming from a physics/UK background I guess I'm sufficiently biased towards journals!