Nice tent Chris
I was inspecting SOAR's and PJMCBear's Bison tents when we were all together at the Delamere meet. I'd just received my Tentipi Varrie 9cp at the time and was interested.
Basically, there are differences, but it's impossible to quantify them as £600 worth of differences. I decided that it was a 'tent for life' and that a couple of years down the line I wouldn't care about the money spent.
The main thing which swung it for me is the cloth colour - I like a light interior.
Talking of which, my wife's favourite Lavvu was the Helsport Varanger because it was light and airy and easier to dry (we don't have a big enough garden to dry ours) and would be my choice if weight was an issue. I did really fancy the cotton fabric this time though.