Of course the two most western countries in Eastern Europe are the two finalists.
Estonia and Latvia are lutheran and culturally closer to Germany and Scandinavia than Poland, so it depends how you define "Western". I would say Slovenia is more Western than Poland as well.
I don't know if you can call that western, but Slovenia is very much alike Austria. When you drive from the Austrian border to Slovenia, you wouldn't expect you're in the "East". In fact, when you drive through it, you see about nothing change but the language and that there are more building sites at old houses.