Even though I've read both books twice, and Master three times (if you count the first time in Russia when I still didn't understand about 15% of the words), I would happily re-read in order to have discussion points.

It's hard to say which is better as both are among my favourite novels of all time. Master might lose by the hair of a black cat, and even then I have a hard time typing that. Pasternak's prose is almost poetic and it is rich, but Bulgakov deftly switches between farce and serious prose, and his serious prose tends to be artistically rich, just as his farce is witty to no end. Both books have levels upon levels of meaning, are rich in symbolism...

Yeah, I'd be very excited if either were chosen. You could even choose Master as the sci-fi selection if you think people would read it. Zhivago is far more realistic. Oh, and if you do choose Zhivago, make sure that people know that the book is radically different from the 1965 movie with Omar Sharif (and so, so much better) and I will know if someone tries to participate based on the movie, not the book.