Kings Dock had a closing roof making it multi functional, more comfortable and probably more atmospheric because of that full roof (as at the Millenium Stadium). It also had moveable pitch too.... to improve its flexibility to host more events all year round. It was a more complex structure in that it was double-decker all the way around with slight over lapping of tiers bringing people slightly closer to the action and offering a slightly broader range of viewing options. It had a proposed 70 boxes compared to BMD's 22 (I think). It's perhaps slightly subjective, but BMD is a more basic bowl. Two tier, but with no overlaps on 3 sides, with cranked straight corner sections and straight running stands, not the more expensive curved constructions as at KD. At BMD the onus appears to have been put on the external design to eleviate heritage concerns and get it through planning and ofcourse the major internal feature is the large home end... so it is a simpler structure. It is also limited in that there a massive initial cost to prep the site, perhaps meaning less cash to increase that complexity.... It might still be more effective design layout in some respects...... sometimes less is more.