All very subjective. In my opinion both the IS F and GS F are good looking cars, but if you are going to state that the GS F looks like a standard GS, then it does so as much as the IS F looks like a standard IS.
As a family car the GS F made more sense for me compared to the IS F, as it had more space for the kids and everything that accompanies them. I came from an IS250 and that was far too small. I think the IS interior has aged well but in my opinion the GS F has a more modern interior, nicer seats, nicer materials and a better fit and finish.
When this thread started, GSFs were selling are lot quicker than IS Fs and RC Fs. Things look to have slowed down now but GS Fs at dealers still seem to sell in good time.
Each to their own and whilst not everyone will agree on which one is best, all three are fantastic cars and a dying breed.