Contentious question... I think it's fair to say even though club Union crowds are the same or less than league, it definitely gets the jump on us for 2nd in terms of media attention and international fans/support.
However at various times during the year sports like cricket, tennis, golf, horse racing, motor racing will all jump into second behind football in the media, ahead of both union and league.
Heard worrying comments that over the past four years some schools in the north swapped from playing league to union after the world cup win. Also recall a big resurgence in the amount cricket was played in schools following the home ashes win a few years back.