Comparing Big Duo with Big Duo Inferno. Hmmm....
The original Big Duo featured autocannons/MG's (I think I remember those); smoke launcher(s); missle racks in upper torso/shoulder area; the 2 high-yield (possibly nuclear at one point); and the eye-lasers.
It did appear that Schwarzwold got defeated due to his own arrogance. However, it's worth noting that he had apparently expended all of Big-Duo's serious ordnance.
Big Duo Inferno featured MG's; drills; and a single eye-laser. Not exactly the most capable load-out for aerial combat it would seem. Note that the shoulder missle racks have been removed; correspondingly it would seem that the high-yield missle stores were also gone. And, like the original, BDI's armour seems to be pretty bad... even the three Union Megadei took punches better than BDI.
Gabriel's plan seems to be incapacitate at range then finish off up close. I think if he had something more to work with than drills, he would have have used the items to weaken his opponent. Was interesting to see the dive attack on Big-O.
LoL @ Big Fau... have you seen the whole series? Under your analysis, it should be pretty obvious what Big-Fau is.
Union... Union... uber alles.