to be honest im more of a gears of war fan im very good at it my k/d ratio is 10.3

Heheh... I've played MW3 for 3 weeks and BF3 for 3 weeks....
Personally, MW3 is, as most noobs said, is spawn die spawn die spawn 'lucky kill' die spawn die spawn die....
It's totally not fun if you are a beginner.
It would only be fun if you could pace yourself with the game.
But for impatient people, they won't stay long.

THEN, weapons are totally unfair for me...
I mean, people with AA Shotgun has a big advantage in CQB.
It would be fair if the AA Shotgun is removed. It would balance the game a LOT!
The USAS 12 Shotgun is also automatic, but it is quite fair.

Actually though, USAS 12 firerate is 360 rounds per minute. The in-game gun is tweaked to be slower.
To my assumption, AA is the real USAS.

FOR NEWBS new to MW3, Always have this kind of Weapon in your slots:
Assault Rifle [preferably ACR or QBZ]
Shotgun [preferably USAS or AA]
Handgun [Revolver, strong handgun]
Sniper [Blaser.... nuff said]
Machine Gun [PKP Pecheneng, it is accurate and has a good firerate compared to other machine guns]

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For BattleField 3, this also features the fast gun, USAS 12. This one really has 360 rounds per minute, but it feels like it is still balanced.

It is a slowly-paced game if you join Conquest maps.
THAT really is slow.
If you want a quick game, join games like DeathMatch.
NOT Squad DeathMatch. Those are for skilled people. Preferably, be in a squad with your real-life friends. THAT will be fun.

I also like how the spawn is positioned.
Some have good spawn positions, but some spawns get you killed after spawning.
Leveling up is also equal.

Unlike the MW3 level-up = Weapon, in BF 3, you have to use a certain class for some time before you get good weapons.
Same goes for Vehicles and Turrets.
If you want awesome equipments for your vehicles/turrets, you have to use it for some time to level your skills up.

Oh, before I forget, BF3 has added a pep thing that when you fire your weapon, it doesn't fire just yet.
If you press the fire button, you will notice that firing the weapon is delayed.

To be specific, there is a 200 millisecond gap, or 500 for Machine Guns, if you fire a weapon.
This will simulate real-life firing a real weapon.

Here is preferred weapons for BF3:
Assault Rifle [AEK, very high rate of fire]
Shotgun [USAS 12]
Sniper [.50 Caliber....]
Handgun [M1911]

Classes vary, but I prefer using the MEDIC Class so I can heal myself...
You also get points if you heal other people...

If you like sniping, I suggest being a Support.
You can deploy an Ammo Box and refill your ammo if you are low on it...
You also get points if your teamate steps on it...

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How's that for specifics.. lol.. jk jk...

Oh, and GAAAAAAAALE!!! http://9gag.com/gag/2736839
It's Lightning! Cuter Version!!!

My job is done here... *flies away*
*Howitzer begins shooting*
*I got shot and my puny wings burst into flames*
*May day, may day*
*BOOM!*
*R.I.P.*

I love BF3! MW3 is dead to me.

favorite weapon list
handgun-desert eagle
assault rifle-ak47 with red dot sight
shotgun-no shotguns
launchers-smaw
tactical knife
concussion grenade
fav perk-stalker