Ok, the Work is 13"hx18"wx5"d.
The Brief is 14"hx17"wx3.25"d. And I've attached a photo from ateliernaff of the Brief with GH.
The reason I did this is that the two bags are of similar dimensions. Most people seem to agree that the GH looks great on the bigger bags (not the First or City). I've seen GH on Mid Afternoons and Briefs, and it does look fabulous.
I think with the Cobalt, the GH will be stunning, but it will be a very flashy bag! If that's what you're looking for, go for it. If you want something a little more conservative, then go for the old hardware.
You can also call the Bal store closest to you and ask them to send you a photo of a RH Cobalt and a GH Cobalt. I know BalNY does this!