If you're in Europe, I would encourage you to go with the Sony. If you ever need support for your e-reader, you won't be able to get it if you buy the Nook. This is really important because anything could happen with your e-reader for no apparent reason. For instance, I brought a Nook classic a little less than a year ago and less than 24 hours after I brought it, the e-ink screen just died for no apparent reason. I live in the US, so I was able to take the Nook right back to a Barnes and Noble and get a replacement. However, living in Europe, that may not be an option for you if something like that happens to you.
So I would get the Sony if I were you. Just my $0.02.