I always think D rings are like a shortened fulmer, so slightly better for steering than just a bog standard eggbutt cheek. Wouldnt think the hook action would be disimilar between the two.
With an eggbutt (with no hooks) there wouldn't be any poll pressure but a D ring puts slight poll pressure (think thats right) plus a slight fulmer action?! Right?!
Anyway I have the exact same eggbutt, and it's fab!