Personally, I enjoy 2142 more than 2 (vanilla).

PRM is excellent for those who love realism and real-world tactics, in my eye's, it's nearly perfect, but I don't particularly like to play it because I don't know how to. There is more emphasis in squads and teamplay, even in vehicles (i believe you now need several crew members in order to fully operate a tank)
POE2 is excellent also for a realistic environments and improved gameplay, but still holds some of the BF2 vanilla feel to it. The maps here feel a lot bigger too, which means more vehicle combat, which sometimes is good, and sometimes bad.

As for 2142, the maps are large which gives a better staging area for combat. The vehicles seem very balanced, even the APC, even though it may not seem like it with the mortar. Though some complain about the lack of tactics and strategic play due to the fast pace, I find that strategy is one of the largest parts of 2142. It's hard commanding because you have to think on your feet. You can't relax as a commander. The flags change so fast and the enemy moves faster still.
Squading is nearly perfect in 2142. Leaders have the ability to talk to the commander, receive orders, give suggestions and recon, among other things. Then SL's can pass down these orders to squad members, and will have several tools with which they can follow these orders.
Also, as some of you have pointed out, there really is no one "all powerful kit" which will own the battlefield. There are different kits for different circumstances, and you must be versatile with all kits or be in a squad in which you have people who are good with other kits. Many people who try 2142 don't like the kit's because there are no specific kits. There are many different tools you can load onto a soldier, but what some hate is the fact that you can't have all tools at your disposal (oh the times when i wish i had cloak, RDX, APMs, and the stabilizer).

... Actually, now I'm lost in my train of thought.. so i guess I'll stop here.