Bad Company is way better than Halo 3.
First off, the least cared about part of games, Single Player.
Sure Halo 3 has more missions and co-op, and Bad Company dosen't have that many missions, but the gameplay, graphics, and humor make up for Bad Companys Single Player. It's fun to screw around on Single Player on Bad Company, just blowing up everything in your way for no reason. The wide range of vehicles make Single Player fun also on Bad Company.
GOLF CARTS FTW!
Next up, vehicles.
Now, Halo 3 has alot of vehicles to choose from, most of them playable on Multiplayer. But Bad Company's vehicles are more detailed and more realistic to use. Unlike Halo 3's Scorpion Tank, it's not like BOOM * two seconds later* BOOM. Bad Company's tanks are like BOOM * 10 seconds later* BOOM. There's a longer delay, like there should be.
Weapons
Again, Halo 3 has a wide arrange of weapons my favorite being the Beam Rifle. Bad Comppany's sniping system is way more realistic, though. Halo 3's is like, if you have a perfect shot on somebody's head, the bullet almost follows them. On Bad Company, if you have a perfect shot on somebodys head, the wind in incorpirated and you have to stay perfectly still for the bullet to hit the person.
Now sure, fags using shotguns the whole game gets annoying on Bad Company, but they don't have that much ammo. On Halo 3, the shotguns have around 40 bullets, eachan inst-kill. Also, on Bad Company, you have to choose a weapon to unlock and time you get a credit, unlike on Halo 3 you get all the weapons from the start.
Last off, Multiplayer.
Bad Company's multiplayer is an auto-win, because it doesn't have any 6 year olds screaming in the microphone yelling " WAHHHHH I KILLED YOU FIRST WAHHHHHHH". Bad Company has mature teenagers and adults, that say "Aww, you killed me. Nice shot." The wide range of pretty much all maps on Bad Company also make it very fun to play on.
Now, if you excuse me, i'll be playing BF: Bad Company.