Ferguson is the better manager, by a considerable distance. Mourinho would be the first to admit that, so the poll results surprise me and certainly don't reflect the community of football journalists and those in the know.
Ferguson built a team up from scratch several times. Mourinho did well at Porto but walked into multi-million pound empires in London, Milan and Madrid. If Mourinho went somewhere like Everton and did just as well, then we could talk about him being in the same bracket.
But largely speaking, this is a poll hijacked by anti-Manchester United hecklers.