Islands, not too much GDI can do once Nod gets a strong foothold in front of their base. I mentioned before that airstrikes will help a lot, but I didn't see many of those in the pug. It's just that: Artys are almost half the cost of meds, and can almost work as a frontline tank as long as they have techs backing them up. MRLS don't stand a chance on their own even with hotties, and APCs get absolutely wrecked. Once GDI can get meds up, their ref is probably already being hit by like 5 artys, and Nod by then should be rolling out flamers.
Walls is a reason why I really want a stank buff. If they had the ability to more effectively deny orcas in a larger area and had better anti-tank capabilities, Nod can get a better hold in the field. I feel that the best strat for Nod is a combined SBH C4 and Arty rush in the early game. If that fails, Nod should do a mass tech+buggy rush, or whatever that is possible to at least destroy any one of GDI's buildings. Late in the game (assuming GDI has a full base) when GDI starts rolling out heavy armor and air, it'll be too difficult for Nod to anything in the field.
Canyon is one of the best flamer maps, and is pretty decent for Artys too. If Nod controls the silo and gets a harvy ad, they can roll out flamers before GDI can get meds, and there's little GDI can do if that happens. Nod on the other hand, can counter meds with an Arty wall.