Of the two, the powershot would be my choice for "candid", because it would blend in better. I have a different, older model of the Powershot, the S-95, and it's performance amazes people still. I find it is actually better than newer Powershots, and has remarkable good built in audio for what it is. Recording times and battery duration on the Powershot are limiting factors.
The camcorder is the better choice for more formal and long-form work., especially where audio is important. it's going to be a little more obvious that you are recording.
Also, if being stealthy is important, consider a 4K go-pro type camera.