BF3 has waaaaay more explosions. The reason cod works as a run and gun shoot em up is that you can always fight through everything. In Bf3, especially on operation metro spamfest there are usually so many random explosions/smoke from m320 and rpgs that you can't fight back. Call of duty also didn't have destructible environments so shooting an rpg at the wall I'm on the other side of didn't do anything, unless it was one of those aluminum ones. BF3 has way more scenarios where skill doesn't get you out. way more deaths from unseen enemies. A CQB map without a drastic change in kit equipment will only increase that.