Compared to the first Bad Company they did a better job with the weapons you can use - you can equip 2 as opposed to one weapon and one gadget in the first one. Also, if you replay a level you can equip ANY weapons you have previously unlocked, whereas in the first you can only use weapons you find on the level, regardless of whether you are replaying or not.
On the down side the campaign in BC2 does a poorer job with vehicles. There's just one stage where you get to pilot a tank and briefly a UAV. The first game gave multiple opportunities to operate tanks, BMPs and even a helicopter for almost an entire level.