From what I've read, graduate study on your side of the pond is a lot better than in the US. I really can't say why. The people I know who got their PhDs in Scotland were, for one thing, really sharp. That helps. For another, it seems there's more of an expectation of a difficult but manageable workload and risk level. Maybe more focus on research and less on politics. Of course, a better safety net, meaning less pressure to drop out if something happens like your spouse or child needs medical care.

Every country is different.