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I like palcomix as well, though in recent years they mostly do loli and shota (I was fine with the teens, but these are more like toddlers) which is really not okay with me when the content is so sexual in nature. Kami tora is a given as well as shibata masahiro, and I really liked CC and Aprion from the old site.
I'm not going to choose a favorite, 'cause I enjoy different artists for different things. Some have cool styles like s-mew and weaver/circe or are just really good artists like fireball. Some have cool and unorthodox content like zae/niknok and Cm_zero (one is unapologetically kinky, the other does fantastic settings and comics with continuity, something sorely lacking in the genre).
It's kind of a boring answer, but if I have to commit, my favorite is probably Kamitora on grounds of having a cool style, being a master craftsman and being a complete fucking pervert.