I think people seem to forget the mrl/artillery are not suppose to be balanced point to point.
GDI vehicles are well balanced when you consider firepower/health/cost,
Nod lacks the balance for benefits, stealth or cheap for weaker units aka light tank
you cannot compare the sides. Nod are stealthy so in a frontal attack Gdi > Nod
sneaky tricks used aka back attacks with Stanks, sbh and pot shot/run tactics ala light tank etc Nod > Gdi
The two main units on nod side which do highest damage is the artillery and flame tank, 1 is long range 1 is short range, but they both suffer with the same issue they have to make there way through gdi frontal attack which as we know GDI have the edge.
the only thing which really effects which side who wins is of course the maps. Some maps are obviously better for certain sides. (i lean towards GDI on this majority of the time) but they can be countered if nod are guess what Sneaky.
in a vehicle fight to give nod the edge we need a bit more open like maps, multiple vehicle paths from base leading into a big open area so nod can do back attacks etc and GDI can still do frontal attacks. (there was one perfect map i know of which had this, but dam i cant remember the name (one where both bases can be attacked from two sides, one was through a underground tunnel and the other side was in a big open area
hard to explain but imagine a circle put gdi at top and nod at bottom of it, the arches are the two entrances one side goes undersground, the other side is outside biggish area, but then a lien cuts horizontal in the middle of the map where the tunnel can lead out to the open area and vice versa
i do recall gdi having them gun towers on it also