Bad Company 2 was made with fun in mind, hence the somewhat funny and sarcastic/ironic campaign. So when you played the campaign with "this is fun" attitude you carried it over to the MP. At least that's how it works for me. This is how BF3 teams feel - WARNING: LOTS OF BAD LANGUAGE - Link.
The other difference being that BC2s destruction is a lot better than BF3s. And there is a lot of destruction going on in BC2. Though maps on BC2 had a major problem of how easy it was to crate a chokepoint and just force the enemy team to stop there and not push further.