DPOA or conservatorship which is better for me to care for my sister?

I have a sister who has a brain injury and seems lucid but is unable to pay bills, or care for herself. I currently am signed on her checking account so I can pay her bills. But because she doesn't live with me, if I need to contact Social Security, etc... I need to drive to where she lives and make the call with her so they will talk to me on her behalf. I'm not sure which is better, a DPOA or conservatorship. I may have to have her placed in a board and care.