Sennet:
2142 I feel handled things much better then BF2, in terms of everything, basically. Lets start with the vehicles.
FAVs and APCs are moot-points - in both BF2 and 2142 you use them to get where you need to go, and as inpromtu cover. Anything else is suicide. At least in 2142, APCs seve another purpose as a Titan Attack Platform.
Tanks are balanced for both sides, even though the PAC one can strafe. And even though they have shields, they'll often only be activated if they know the shot is coming - often after they've been hit the first time too. The shield will basically last the course of a reload - they'll shield will be gone in time for the next hit. They only take 3 hits from the starter kit from the top or sides, 2 from the back. Philum makes it one in the back and 2 elsewhere.
Walkers are powerful, but they become huge targets, and they have to huge weakpoints - the back and in-between the legs. One good basic Rocket or Philum ends a walker a lot of times.
Air vehicles in 2142 are fairly balanced. The gunships are powerful, but in order to make the most of them, they have to move dangerously slow for some time, allowing any Enigneer to line up shots from multiple angles. Also, Motion Mines on the Titan Hanger Shield never gets old. Unlike the jets of BF2, which are invincable, flying death machines who scoff at any attempt to combat them.
Further, for ground-based targets, Engineers have the Motion Mines, which unlike the useless mines in BF2, actually track the target, and though they do slighlty less damage then normal mines, 2 or 3 will destory anything.
In addition, for maps heavy with air units, the Engineer can get the SAAW in 2142, which is an excellent anti-air tool. Though ineffective against ground targets, its better then the options of....absolutely nothing in BF2 and BC.
Skilled players know that both the Philum and basic Rockets are the most dangerous weapons the Engineers has, and with a sufficently skilled user, the starter Rockets in the Enigneer Kit are more dangerous then the Philum.
Further, unlike BF2 and BC, the ground turrets actually dangerous to vehicles. The rail gun hurts....a lot. The anti-air tracks well, and does a huge amount of damage. Unlike in BF2, where you're just another point on the scoreboard if you even try to touch the AA, or in BC, where the AA just tickles the Helios, and the ground turrets are too easily destroyed and never come back.
Including this, BF2142 was overall just a better game then BF2. Hell, I'd pay for 2142 all over again if it came with the Frostbite Engine.