It certainly isn't RSA even though they are the best test side in the world (IMO at least now).
India has lost 2 series in 2 decades and this will be India's first series loss in this decade which comes v RSA pretty early into the decade.
Australia is pretty strong at home too.
My cousin and I just raised this topic when discussing cricket without going into the details. Richard had said India is the stronger side at home giving some reasons not that long ago, if I am not mistaken.
EDIT - Mods, add a poll please.