I vote for option B, renovate the hallways.
Our hallways are very old and dirty. The carpet has many stains and in some places it is broken, so people can trip on it. The walls color is old yellow and there is scratches everywhere from people moving furnitures. When my friends come to visit me, I feel little embarrass.
Also, the lights in the hallway are too dark, special in the evening. With new LED lights it will be more bright and more safe, and it will use less electricity, so we can save money for the building.
I think new hallways will make our building more nice and also more valuable. If somebody want to sell their unit, it will be easier with beautiful hallways.
About cameras, I think our building is quite safe. I lived here five years and I never had any problem. So for me renovation is more important.