Furst is an amazing historical writer with an uncanny ability to evoke mood. And he's working from scratch to create everything fictionally. What he tries to do he does incredibly well -- at least as well as Graham Greene. Orwell is a social critic, a journalist, his era's equivalent of a blogger, and he's unsurpassed in nuanced social observations and analyzing class distinctions. You'll never go into a restaurant again with the same attitude after reading about kitchen life in his "Down and Out in Paris and London."
They each do extremely well what they set out to do. I don't like ranking writers; I much prefer enjoying those with a well-defined genre who do it well, and each one excels. Wodehouse, by contrast, is less ambitious, more formulaic. Funny as hell, but predictable.