If you're already a pro at playing the guitar, you will find the 6-string banjo identical in every aspect to the playing of the guitar. Decay of the notes will be the only difference, with 6-strings having no sustain. This would allow the guitar player to transition directly into the banjo.
You can imitate playing a 5-string on a 6-string banjo, however it will never be authentic. The 6-string and the guitar are tuned entirely different that the 5-string which is tuned in open G, the 5th string being high G octave.
The 6 string goed have a good bottom end, which will support melody and other lead instruments. The gauge of the strings on a 6-string banjo are also thicker which may help in ease of playing. However, there still isn't a fifth string drone which is the key element that gives the banjo its sound and character. A couple other negative aspects of the 6-string is that the gauge of the strings is a bit too light to allow bottleneck playing, and also there isn't a bottom end to support other instruments or support playing blues solos effectively.
