With nod, I utilize heavy air support and the obelisk, along with cyborgs. Banshees and cyborgs help me control enemy air threats, and along with the obelisk can lock down a pad or two from most vehicles. I use the Inferno to hit enemy infantry, and the fire can help block parts of the board temporarily. The biggest downside is the slowness of the inferno and losing it, but I I'm thinking of replacing something (attack bikes probably) in my lineup with the flame tank because it can take hits while eliminating infantry threats. That way almost all of my bases are covered.
At any point, I'll have 1-2 banshees, 2 infernos, and cyborgs on the board. I might be able to trade a flame tank for an inferno, but 2 infernos make a wide area inaccessible to infantry. Backed by an obelisk and anti-aircraft, they can lock down a significant chunk of real estate in the middle of the board. The actual balance depends on what the opponent throws at me. I'll build more inferno's if they're deploying a lot of infantry and light armor, more cyborgs for lots of anti-aircraft units or heavy armor, and banshees/cyborgs if they're aircraft heavy like me.
IMO, GDI's air support sucks, at least in the lower levels. Their air defense also is lacking outsider the hover MLRS when you consider the disparity between nod and GDI air units. You can't obliterate a GDI opponent with nothing but aircraft, but you can make life hell if they can't deploy zone troopers fast enough to take on two infernos.