This subject just happens to be a subject I'm pretty familiar with! I have designed my own paintball marker. We are still testing it, but I've also designed a new style of play.
First off, the gun, 4 moving parts, select fire, ROF of 1300-1500 rounds per minute. I still have heat issues with it as you might suspect. I will sell the manufacturing rights to whomever offers me the most for it once I solve this heat issue. Some sort of governor may be required..... Otherwise it's totally consistant, puts out all rounds at 275fps or so,with a max variance of 3 fps either way. If you really want, you can put it right up to 295 or so and be within the safety limit, and it will stay there, no real need to rechrono it, even though we do anyway because that's just good habit. The nice thing is though, with that consistant velocity, and the design of the gun, it fires about as accurately and as far as most pumps. Anyhow, as soon as I get the heat issue worked out, I will patent it and then you guys will get a look at it, but until then it's super secret
Anyway, the new gameplay style is to have each squad using this gun with spring-loaded tube mags which hold 20-30 rounds. This teaches incredible fire discipline, because up to 1500 rounds per minute can eat up ammo very fast, so it's tempting to spray and pray. You literally can just "catch" someone with 10 rounds in a burst, but if you miss them, you gotta reload, and the way we have it configured right now, you reload it a lot like an AK. One person in the squad sometimes uses one with a full 200 round powerfeed hopper, he becomes the squad machinegunner. Also, sometiems we use water balloons with a bit of food coloring in the water to simulate grenades, but it's not a perfect system.
As for Airsoft..... Airsoft has a lot of plusses and minuses. The plusses have been pretty clearly spelled out in this thread. The minuses are that A) the BBs are not environmentally friendly, paintballs are. B) The BBs do not handle wind well at all compared to paintballs, think .22LR versus 50 BMG at 1000 yards. C) BBs do not penetrate cover at all, not bushes, not brush piled around bunker windows, and not guille suits(good luck even knowing you were hit in one of those) D) BBs have less mass, they do not perform out to the same distances that .68 cal paintballs do.
Airsoft is great training on some levels for handling realistic weapons and fighting in close quarters with them, but paintball is more realistic in a great deal of other ways. The main way paintball is less realistic is the stupid culture within the community of demilitarization. A lot of paintballers do not want to be associated with cammo-wearing recball players. They don't want anything to do with the military. I loathe this attitude, and it's a big reason I only play with my friends/testers, and don't go to the nearby field.
Things I have learned from paintball:
Towers in bases are not effective. The enemy knows right where you are, and they take full advantage of that fact. The rules change some if you have a team roaming around the base keeping the enemy too disorganized to deal with your position....
Bunkers are not effective without a really good clear fire zone surrounding them.
Hiding in trees is a bad way to engage an enemy. If you hide in a tree, stay really well hidden, and have your friends engage them on the ground, and then in the chaos, put rounds in their backs.
Penetration matters more than accuracy. As stated above, I would give a lot to have my paintballs magically able to penetrate heavy cover like real bullets do. Part of why I prefer guns like the FAL, or the AK-47 over the AR-15 or the AK-74 is my experience in paintball. I want a gun that will go through what he's hiding behind. My chances of actually catching him in the open are not good, unless maybe I'm in a desert....
Sound makes a big difference! If your enemy can hear you, they can track you. You can use this to your advantage if you're smart about it.
Ruses are good, but don't overuse them. Use them only enough to keep your enemy worried about you using them. Chaos is your friend when it's dealt the way you want it to be.
Aimed fire has some advantages over spray and pray, but aimed spray beats either.
Explosives are often more valuable than your gun, but without your gun, getting into a position to use your explosives is hard. Use the gun to pin them down, use the explosives to take them out. Works fairly well, but it has drawbacks if they are doing it too....
As a rule of thumb, if the enemy begins to imitate you, change how you play.