I don't agree with this. Dostoevsky's characters are philosophical archetypes, vehicles to express particular views or psychological states he wanted to explore. Tolstoy's characters are not such representations of ideas, but actual rounded human beings.
If you come away from reading The Idiot thinking "wow, what a tiresome, failed philosopher", with all of its multi-page mouthpiece rants from characters about how the Roman Catholic Church is evil or whatever, I can understand that. If you think the same after reading Anna Karenina, I don't really know what to say.