The most use I have for fretted fives is having two octaves in one hand position, that is handy for pit work, transposing songs or synth lines below the range of a four. Playing standard lines I like to have all the inflections, slides etc. plus the different timbre you get playing up the neck, more fill on the thinner strings and no extra string to mute. I would consider the high C on a six the preserve of chords or soloing/solo pieces...
One advantage I've found is fretless. Lower notes played up the board equals shorter scale, easier intonation than the very bottom end of the neck.
I'm more likely to go for the right timbre rather than convenience though, even if it means a bit more work.