I own both... Profoto B1's and the Eli Quadra set before the renaming. I also own 2 Rangers. I use them on location for weddings, onsite corporate work and family portrait sessions. I use the Rangers in studio and occasionally use the Profoto in studio too. Not sure about the others above but I have abused the hell out of my Elis and now putting the B1 to the test of this current wedding season, so far no issues. I've had the Rangers about 6 years, Quadras about 3 and the B1 about 8 months. I really do torture test my gear... on site, beach, desert, California Redwoods, etc... Not sure about what PWP is talking about up there as the B1 are still quite new? My B1's are pretty solid and I like the battery because it is usually high off the ground on a boom or stand so it stays nice and dry. I never use ETTL so that wasn't a big draw for me but YMMV.
Of all of them, I still think the Eli Quadras are the best on site for size and utility. I like Profoto modifiers the best, Elis are good but not as beefy as Profoto. I have modified all my brackets to take the weight off the Eli's though.
I've used the Buff's and although nice... not a big fan of the color inconsistency between flashes. Also feel like the mods they have are cheaply made and replaced quite a few umbrellas before giving up on them.
Eli Quadras
Profoto B1
Eli mod...