I don't have both but I've drove a fair few of both examples, I'm a little biased towards the 7 because I own one
but I liked the little sharp revvy engine in the 7 more and the 6 felt a bit wobbly and lazy body wise, the GT 6 is definitely faster and more comfortable especially compared to a 140, stick front and rear braces and maybe even a lower rear brace... Lower it and the 7 just gets even more solid and loves the road
but I also like the interior of the 7 more... It's more compact like an Mr2 people say, the centre console and arm rests etc come quite high up with low seats... The 6's didn't have that... But then a + for the interior of the 6 is it doesn't rattle as much lol
I've tried to keep this as professional as possible and not start no 6v7 arguments we all like Celicas here but for different reasons and we all have different tastes