I bought an 11'6" to start with. It was fun but I got sick of lugging this huge thing around and lifting it into my garage board storage rack.
I live 600m from the beach and I could just make it to the beach carrying the board on my shoulder.
I now have a custom built 8'11" surf SUP and it weighs 5.6kg. I can easily carry it down the beach and it's great in the surf. It fits in the car for trips down the coast. It's ok on flat water, a bit like riding a mountain bike on the flat instead of a road bike.
I still have a hankering for a 12'6" raceboard for doing downwinders and getting the great feeling as the board slices through the water as I flex my glistening muscles in the sunlight like a tribal warrior. (Excuse me while I have a quiet moment alone.

) Maybe when they get cheaper and lighter (sounds like some women I know.)