Fatih,
I've never owned or driven a GT-3 on the track, so I can't really say. You message that the GT-3 is actually easy to control at its traction limits is actually contrary to everything I've heard from others.
I can say that in my short track career (22 track days) I've noticed that GT-3s seem to crash and/or go off with much higher frequency than any other model. I've seen two go off, one right in front of me while entering the bus stop at WGI, another right behind me coming through turn 10 on the Monticello South course (reducing radius, we both came in off line because of a late pass). This observation could be caused by the high penetration of GT-3s at track events, or because they have so much power, I don't know. But the big picture suggests that these cars cross the line easily.
I'd encourage you to gather some more seat time before sending too strong a message of how easy it is to go fast in a GT-3, only because folks may read too far into that message. You spent a lot of seat time in a Cayman, learning all there was to know about performance driving, analyzing your technique, sharpening, honing and polishing your skills. So for you, the car may be easy and fun. But I shutter to imagine a track newbie with a big wallet and a small driving resume taking the plunge into a GT-3 missile because he read that it's faster and easier to control during a slide than a Cayman, when the Cayman may be a much safer choice for that individual and his/her skill level.
My point. You do have a magic skill. You know how to drive...
You did it right. You learned in a car that is truly forgiving, that has moderate power and lots of safety systems. Then when you were fast and knew how to drive, you moved to the more powerful and understandably more dangerous track weapon, the GT-3. So for someone with your skill level, the GT-3 may be easy to drive fast. But think about some of the students you've had... What would happen to them if they had 400+ hp and a less balanced chassis...?
Just some food for thought.