I have played 4, 5 and 6 strings extensively over the years and agree with the OP that I never had much difficulty with any of the transitions.
I have settled predominantly on 5 strings because it really works for me in a band setting. transposing key etc. Although I enjoyed playing 6 strings I personally found the high C to be redundant all too often with the styles of music that I play live.
Its all good though, music is art...there are no rules.