Rocca
I'd agree the XT660Z is a very capable and fun bike to ride and can lead you into temptation on twisty lanes
The 1200 is a lot more stable and has a lower CofG where I sometimes found the 660 a little top heavy if wrong footed (though lighter than the 1200 obviously).
Still getting to grips with the 1200 though it may take a while with the winter closing in and the roads being a bit skeitie (wet and potentially slippy underfoot or tyre). Suspension wise you can see yamaha spent some cash on the 1200 where the 660 was built down to a price, same could be said for the bodywork fittings. though they could have fitted similar indicators from the 660 to the 1200 as the stockers are a bit cheap and nasty.
Side stand on the 1200 is my other gripe, its seems a smidge short and not easy to get down as my pants keep catching the peg as I swing it out.