I play GDAD unison strung. Unison strung is better for tunes than octave because the tune's pitch gets confused when going on to the lower courses. I also prefer it for accompaniment as it gives a fuller sound. GDAD is great for playing in the folk friendly keys of D and G. With this tuning I find that I can play chords and suggestions of the melody simultaneously or chords with linking note comprising the melody. I think GDAD is popular with Irish bouzouki players and is the tuning of choice for James Fagan.