Union appears to be more physical than league or at least closer to the level of physicality in American football (at least in trenches). Even a union scrums are more physical. Whereas a league scrum reminds me of an uncontested union scrum or a 7's scrum (not a huge fan of 7s). Plus, I enjoy watching players attempt drop goals (which is only worth 1 pt in league) and mauls (especially driving mauls).

Then again I probably was also influenced by what Setenta was broadcasting on TV at the time. In terms of league rugby, Setenta aired Super League (UK) and NRL. On the union side Setenta would air Aviva Premiership, Currie Cup (SA), Air New Zealand (now Mitre 10), Heineken Cup, Six Nations, and Tri Nations.