For me really the choice was easy, i did not find the GS to be appealing at all, the interior is not as luxurious as the ES, not as practical as the ES and the rear as well as front spaces is too tight for me. The driving position as well was not very comfortable as i test drove both cars and found the ES to be my choice, i am 6'1 feet, so for me in the GS there would be virtually no space for the rear passenger but with the ES, there is plenty to go around.
I also found the ES to have a more luxurious stance than the GS which had a more sport oriented stance, lets not forget the panoramic roof on the ES which gives it a very sexy look.
For those who mention handling on a rear wheel drive is better than FWD, i dont know about you guys, but i dont drive like a lunatic on turns or curves, i drive a car with respect, so wether it was FWD or RWD does not matter as i am not going to be driving it through cones or going from 0-100 only to brake back to 0 again.