I'm no expert, but I've run 180s and 190s on my 999S for some time now. I felt I was getting too far off the edge of the 180, but I'm sure that's just my own feeling, an expert would no doubt disagree. With the 190, I never get to the edge of the tyre at the back, although I do seem to be running out of front. Again, I'm sure that experts will tell me that I'm in no danger there.
I like knowing that my rear contact patch is bigger with the 190 and have more confidence in it. The slower steering that the 190 supposedly produces is easily dialled out (in my experience) by making sure your front and rear ride-height is sorted properly.
My 2p-worth and worth the investment
Have fun playing Glyn, you'll find out what works for you - of that I have no doubt.