http://www.angusbeefbulletin.com/articlePDF/By%20the%20numbers%2001_09%20ABB.pdf
And, you've pretty well pegged it. Most (not all) high positive $EN cattle will be smaller mature size and with lower milk epds. For a reason.
Milk is not a maternal trait, it's a growth trait - there's a feed cost associated with it.
Frame requires feed to build.
$EN probably should not be a single-trait selection criterion.
I 'chased' high positive $EN for a while, but I'm not convinced that it's even worthy of consideration in our current management scheme - but if I'm using Angus sires, I still try to go with a positive (above $0) $EN, if other criteria are satisfied. We're a commercial outfit, selling stocker/feeder steers; don't have any idea how/if/why $EN would have any concern to folks producing fluffed/blow-dried show cattle.
Probably if you(generic) were running cattle on grass and winter hay feeding of hay only...$EN might be important. But if you're gonna feed corn sileage, a grain ration, etc...I'm not sure it's applicable.
Look at the Green Garden Angus cattle - they'll be low-frame scores, and moderate milk, with way above breed average $EN - but the Marbling/Ribeye/Tenderness are there, with high $W and $B. Wish I'd bred more Gardens Wave daughters...