It all comes down to personal choice really. I play GDAD double (unison) strung, but then I play to accompany singing and tunes, mainly. GDAD gives some really easy but effective chord patterns, but you are playing in an open D (sort of) tuning, and you need a capo to be as effective in (most) other keys. I don't play a lot of tunes on bouzouki so I'm not the guy to tell you much about that side of bouzouki.

It might help if you told us what you are hoping to do with the bouzouki and then people can give more structured advice. But for accompanying stuff - well, I'm very happy with my setup.

In the meantime, my advice is - play ofetn and experiment!

Good luck, Les