I'm a NOD player myself, but i teamed up with a few experienced GDI payers over the years and i've seen GDI do wonders vs. any target.
Learn how to use the zt (zone trooper) properly... one of the most underestimated units in GDI.
Do not use Kodiaks just because NOD uses Salamander... use GDI tools properly.
With NOD there are quite a few useless units once u get the research done on a select few. Who uses bikes, reckoner, black hand or even militants?
GDI requires more fine tuning and is more powerful overall... It has more options in my opinion.
The only downside is the repair time.
The units speed is also a big factor to consider when playing GDI... Send in attack waves to take advantage of the units speed.
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If Kodiak aura would protect air units also:
What happens during GDI air units vs. forgotten upgraded mgs. (fort attack)?
I would suggest instead a stronger aura (longer duration)...