I used to use GDAE because I started on the mandolin, and tried to transfer my skills (or more accurately lack of skills) in picking out the melody to Irish tunes to the bouzouki. I immediately ran into problems because of the long scale length and consequent hand stretching problems, it's very difficult to play fast.

After a conversation with James Fagan last year, I started using GDAD instead. It's much better for chord accompaniment, and I think I'll leave the Irish picking to the mandolin. Like James, I now tune in unison rather than in octaves. I had to do this to copy one of his songs, and it gives a fuller sound. Andy Irving and I think Donal Lunny also use GDAD.