Guns: Tier one special operations groups such as 1st SFOD(Delta Force) and SEAL team 6
Killing style: Spetsnaz, they have inhumane ways of killing people
Even though SEALs are hardcore and go through brutal training, I think they are overrated. I think Delta Force is underrated because they are so secretive. In "One Bullet Away" by Nathaniel Fick, when his platoon first enters Afghanistan there are special operators talking with eachother. SEALs, SAS, and "Boeing Contractors" which are Delta Force, with a secretive name. Delta isnt even recognized by the US government. Nobody even knows the real training they go through. Everybody knows what SEALs go through, and therefore everyone knows they are hardcore. If it wasnt for Black Hawk Down(the movie), very little people would know who/what Delta Force is.
The mission: I think the Marines have the best mission. They are told to take a town and they raid and kill. They kick down doors, blow up houses and their mission is to just look for insurgents. Army has to provide security and take hold after the Marines ****ed the town up. If I could become any special operator, I would be a Force Recon Marine becuase they arent cocky like the rest of special oprerations, and their mission is better. Delta Force's job is primarily to rescue hostages, as told through Black Hawk Down(the book!), and SEALs have a variety of missions, but hostage rescue is in there. I am not fond on hostage rescue, because generally its a civilian reporter they have to save or some shit like that, and if you **** up the rescue, your screwed. Going deep into enemy territory, getting recon and getting out, killing people silently on the way sounds sick.
I cant say whether any is more badass than the other, because they all have different missions to accomplish and you cant really compare them.