Depends what you mean by difficult. In my experience, northern European women are a bit more difficult because they are very independent, and have all sorts of feminist ideas. Eastern European women are more traditional in regards to gender roles and I find them more pleasant to engage and deal with. Also i find eastern and southern european women more feminine than northern and western. Just my personal opinion.
That said neither is necessarily a bad thing, just different cultures, and you will find different women everywhere. I'm sure there are northen european women which are very easy going and traditional and hard to deal with eastern Europeans. Can't really generalise on this. Different people, different upbringing, different ideas, different personality etc.