Really there's no reason to be super-obsessed with comparing the two difficulties. The reality is they are different progression tracks and should be treated as such. Sites like raidranks are properly separating out 16-man vs. 8-man progression and that's as it should be.

As far as I can tell, the general theme of 8-man vs. 16-man is:

(1) Enrage is easier to beat on 16-man, and it's easier to change up your operation composition to simplify things (e..g, you can use 3 tanks on fights if you need to).
(2) 16-mans sometimes need more coordination.

I think (1) and (2) tend to balance out for the most part.

Overall they've done a pretty good job of tuning things. The fights can be beaten by competent coordinated groups on both 8-man and 16-man.