I play in Advanced mostly, although I do foray into Nation, Casual and occasionally 1x1. Most sections have something to offer, but I generally look for is character development, a touch of realism, and a pace I can actually keep up with - generally speaking these three things I do not find in the Free section often, so I almost never go there. I feel welcome in any section I choose to write in, I would say Nation has a bit of reputation for being elitist (or at least used to), but its never been a problem for myself. 

But honestly its not about the sections, its more about RPs individually. On the old guild the best RP I was ever in was in Casual, went on for years and had really good post standards and great players. It was well above the quality you'd expect of Advanced. So yeah, books and covers and all that.