I think theres a distinct smell of something in the air. I feel fairly qualified to answer the query, as I have a Cup now, and used to have an ITR until about half a year ago. Did 26k in the ITR, and used it on track as well as on road. Used the AP22 accelerometer on both cars on the same road.
The ITR is very, very good. Driving position and gear box are superb, engine, chassis, suspension likewise. A very good package. The Clio has a worse driving position and gear change, but, and I say this with no hesitation whatsoever, it is just as fast around the track as the ITR was, and there is not much in it in a straight line. The Cup clocked 6.64 seconds 0-60, and the ITR 6.67. 30-70 times were identical at 5.9 seconds.
I have to admit I was somewhat unconvinced after buying the CUP as it is more unruly on road than the ITR( which is more balanced ), but once out on track the CUP is a fantastically adjustable, accelerative tool with brilliant brakes. I cannot comment on the standard 172 much as I havent driven it on track, but it is more sorted on road than the CUP. Horses for courses, I guess.
The CTR is a different, have only driven it on road, and again was impressed. It is not as focused as the ITR, and not quite as adjustable either, but very fast, grippy and easy to drive.
Good cars all of them.