On the weather, that is the worst I have seen since I have moved to the UK. Friday night was freak conditions, I think I've maybe seen one or 2 games of RL with worse conditions than that, one was Cronulla vs Newcastle maybe in 1998 or 1999 at Shark Park. I don't think they would have advantaged one team or the other, as remember the Super League is played through the English summer. Furthermore, there was a comparison of Melbourne and Leeds weather in the match day program, and rainfall wise they are very similar.
The wind and rain was so bad, both teams struggled whenever they through the ball wide. You never knew which way the wind was going to gust. Both Slater and Webb, and also Lee Smith on the wing were amazing under the high balls.
Furthermore, I have no doubt the top English clubs are as strong as the best NRL teams. It's a matter of finance, Leeds can spend more money on players, and hence have guys like Lauiti'iti coming off the bench, who would start for any NRL team.