I would just go for your first choice - the Wam 6.0 2011 - without thinking too much about anything, but getting out as soon as possible and enjoy the waves
It works really well according to everyone (and me), and is quite floaty/big for its size, so you can use it unstrapped very well too (or strapped - whatever you will end up with).
I have ridden the 5.10 as a good size, but am only 75kg.
It will most likely not be possible for you to determine what you want anyway - what you seem to be fully aware of.
So the Wam will work great, and you can even choose between thruster or quad fins, to change the way it feels.
Just to make things easier
If you had written any other board on top, that was well-known in terms of size and feel, I would also recommend it as your first board.
I dont ride these boards myself (got custom waveboards from Ralf Bachschuster) - but usually always borrow and test both North and Wainman (and a few others) a lot, when the new waveboards arrive