I saw a white F Sport yesterday when I was picking up a LC500 for the day. They also had a silver one in the showroom and I saw a green one on the road a couple of weeks ago (neither was a F Sport)
I like the Sonic T. It is very smart, exclusive to Lexus and will stay clean for longer. On the other hand, the white looks more sporty, and arguably better with the darker wheels of the F Sport. Somehow makes the car look bigger and more imposing.
Have you checked Lexus online configurator? - It gives you a reasonable idea of what the car looks like in either colour.
Also to consider, if it matters, the white option is £670, sonic T is £920... according to the website.
Note that F Sport white is not a flat white. It is metallic (not pearlescent like the Sonic White available on the Takumi grade), although you only really notice this in the sunlight.