A330-300 @ 5600 nm -> A350-900 @ 7500 nm = +34% range
A330-200 @ 6700 nm -> A350-800 @ 8600 nm = +28% range
It will be interesting to see how Airbus will grow the range of the existing aircraft approximately thirty percent. The A330 is still a relatively new design (it was authorized in 1995, nine years ago) so to make this big an improvement in a relatively short period of time will be very impressive.
--ev--