It depends on what you want:
- control and be able to tighten your turns: thruster
- faster but more drawn out turns: quad

This said, I recommend the Quobba fins in a thruster setup. With their added speed and hold, you get the best of both world.... and you will not want any other fins once you try them.
I use the M (orange) on my 8'4" 120l (I am 100kg) as they provide enough hold at speed. But if you tend to surf at lower speed, you'll want to wait some days for the L (black) to be available. I use the L on my small wave boards.

I'd add that for the quad setup, SUPs seem to work better with very small rears. Much smaller than the ones recommended for prone surfboards.

Seajuice said..
Agree Colas. I found that my Sunova board came with a smaller rear in its thruster set up which surprised me at first.

Yes, note that the excellent classic Al Merrick thruster set always had a smaller center fin. As the Harley Ingleby, even though designed for longboards.
Since you can mix and match FCS sets when buying them, I tend to buy larger fronts than rear. For instance, the lastest 5-fins set I bought was the Jason Stevenson on,e but I bought the sides in L and the rears (quad + central) in M

And this is what I use in my small wave board with the Quobba: L side + M center: