[London] Tube question

[nou]

If you were going northbound on the Northern Line and wanted the most efficient change to the Bakerloo Line, would you do it at Waterloo, Embankment, or Charing Cross?

I asked bob and he wasn't sure. Looking at the Tube map, the only station where the Northern and Bakerloo lines are on the same “blob” is Charing Cross — but am I misremembering that blobness is related to ease of changing?