It's you car and your choice, and as such advice is rather limited, more a prospective from other owners.
Trying any of these cars for a few hours is not really going to give you a proper prospective. You really eed to know yourself what you want the car for as they are very different.
As some have said the GS is smaller, more nimble, quite sporty and a decent GT.
The GT on the other hand is a much larger GT, swift and softer all round.
Both fit four comfortably with the GT having the endge on comfort.
Running cost are broadly similar, GS is cheaper but requires more frequent services and has a clutch, the GT less often but parts are more. But the GS will not depreciate.
I have had a number of chats with people in a similar position and it comes down to what your longer term use is. Try them both... stick to your budget and dont get too hung up on power, engine size they are all lovely cars.
Good hunting.