I just realised something quite uncomfortable. I can't be objective when I think about the cultures, mainly because I've been M-E roleplaying for so long that the thoughts and opinions of the character I've played longest have started to affect mine.
I actually like all the northern people, no matter whether they live on the western or eastern side of the Mountains. However, Beornings are my favourite - mainly because of Beorn. Bear is one of the animals I like the most and I wouldn't mind living like Beorn: in a big house almost in the middle of nowhere with a lot of intelligent animals. And those honey-cakes, of course.
The others I like much are the Rohirrim. I've been riding more or less frequently since I was three, and about a year ago I found a stable where they teach riding in medieval style and fighting skills, and it's wonderful. Archery, fencing, spear, lance... And everything on horseback. Not to mention those stunts: picking an object from ground in gallop, hanging head downwards from the saddle, jumping over a burning obstacle... I love it.