These numbers get all balled up depending on whether who writes them includes brackets, lamps, lamp covers, etc.
The basic Einstein housing is 4.75" rounded square and is 5.625" long. The lamps and glass dome take it to 7.5" long and the mounting bracket takes it to 6 1/2" high.
By contrast, the AB housing is 5.3" slightly rounded square 4.75" long. Don't know who published the 9" long . . . it's more like 8" including the much longer modeling lamp. May be 9" with lamp cover.
Visually, I'd say the Einstein looks a bit small than AB. I design them as compact and functional as possible, and personally believe the Einstein form factor to be more ergonomic and visually pleasing.
Einstein housing is more reenforced, the accessory mount is vastly improved and it has much improved cooling to accommodate the faster recycle and 250W lamp. Some on DP Review think they are ugly, I think they are elegant and the that Profotos are ugly round tube with no aesthetics at all. To each his own.
http://forums.dpreview.com/forums/read. ... e=34186635 what fun they have over there.
I know we have 1600 pre orders for Einstein since we started taking them a week ago. This is maybe what Elinchrom or Profoto sells in the US in a year . . . (I don't have their sales data.)