I like the score streak system.. but I also liked having the option for support streaks like in MW3... was nice for those days you couldnt kill a dead cat..
I prefer scorestreaks. I like the way capturing a flag or hardpoint works to your next scorestreak reward. I miss the Specialist pointstreaks from Modern Warfare 3, and I think it would be interesting to see it in Black Ops 2. I know it won't happen, but would still be fun to play :p
I like killstreaks better personally. I mean if I am playing towards getting the K-9 unit or swarm I hate that I have to either risk my life to pick up several tags and I can't just play the corners of the maps and dominate the other team. And before any of you say you're suppose to play the objective, blah blah blah, I usually do but it is always fun to just kill whore every now and then.
Score-streaks are certainly the superior system. With kill-streaks, there really is no incentive to assist your team or attempt to actually achieve or capture objectives. Rather, one can succeed by simply ignoring objectives and killing as many enemies as possible.
In Black Ops II, there is much greater incentive to assist your team. Score-streaks reward you for capturing the flag or the Hardpoint. You get rewarded for assisting your teammates and destroying enemy equipment. All of these things are important and ultimately help bring your team to victory, and therefore should not go unnoticed.