Hazy,
Your description gives the impression that after your one hit-up and your three-metre burst of the line you do no more running in league!?
Come on, be serious. I don't think anyone who is being honest with themselves can say that, flanker or not, there's more running involved in union than league. Nobody. It's just a fact that league requires more running as there's less players on the field, the ball's in play at least twice as much and there's a 10-metre offside gap. That's just the laws of the game. Add onto that the greater amount of tackling in league and the constant going to ground and getting up again (the real killer) at tackles and PTBs, all of which make league - by far - the more physically demanding game. (And I'm not even getting into the greater ferocity of collisions in tackles compared to union, I'm just talking about the cardiovascular demands).
All union converts to league at the pro level admit that the most shocking thing is the phhysical aspect and how long it takes them to get used to the conditioning element in league.
Your description about pressuring the 5/8 and getting to breakdown is fair enough (I've played far more union than league and my initial position was flanker, then moved to centre) but you fail to mention that this is a fraction of the total time of the game. League running is constant.
Technically, in the areas the two games can be compared, league wins hands down. Passing and tackling. Of course line outs etc are union victories as league doesn't use them!
League produces better ball handlers and tacklers, and better team defenders and off the ball runners than union. I don't see many league teams crying out for union technical help whereas the opposite is certainly true.
Your point about distances between defence and attack is also misleading in my opinion. Union defences are behind the back foot but union attackers are deeper whereas league attackers begin barely behind the PTB. In my experience, due to the speed of the game and the constant need to readjust and attack again and again you have to think quicker in league. In union you've just got too much time on your hands ever to get pressured. And if you do lose the ball, then so what, whereas in league possession is paramount therefore the pressure on players to make the right decisions and to be technically sound is far greater.
Anyway, thanks for an honest and well thought out answer, even if I think you're totally wrong and just being a rah rah apologist!