Best is relative, if you are using a Switcher like the ones from Black Magic Design or Newtek you can use any HDMI camera that outputs a clean signal. A used Panasonic GH2 or Sony A5100 would be inexpensive and give EXCELLENT footage as a face cam. I've got the Panasonic G7 , it does 4K and is pretty affordable. My friend at Mad Mohawk Films recommended it.