Each of these vehicles are distinctly different from each other; they carry different weapons, are more/less manueverable, are stronger/weaker, etc.
The gunships and Transports have different types of gun turrets, one has a mini gun essencialy and the other a slower but heavyer hitting gun.

You also forgot the Titan (4 lower turrets and 2 upper turrets), AA ground Turrets and anti-land ground turrets, which still technicaly count as vehicles.   FS only has the E-Web.

The Carrack (the small imp cap ship, forget which one it is), and the Corvette are identical both in terms of armorment and I think even turret location.   The Nebulon-B and the large Imp cap ship are Slightly different in location of weapons.

Another thing you failed to mention is how many of these vehicles are avaliable in each map.   On Land maps FS only has 5 vehicles, 2142 has 8-13 (depending on if its a titan map or not or if land only, not counting expansion vehicles).    In space maps in FS you get 12 different vehicles (since smaller caps are identical and you forgot to mention the healing ships), and ZERO customization.   You play as one of those 10 ships and thats all you do.  There is no changing load outs, nothing other then a Pistol that you cant even use for anything.

So untill you bring some of those Space Vehicles down to the land maps, include more turret options and provide customization (preferable land fighting) in space maps 2142 DOES have the advantage.