By your logic then, the 1.6 16v Clio is a limited edition. There were less of those sold than Cups......
Lets not start a Cup versus 172 debate again. Lets just answer the guys question without ant personal input. Ill (try) to go first.
The Cup is the same as the 172 in that it has the same engine and gearbox. The Cup version was stripped of non-essential items such as;
Xenon headlamps
Leather/suede interior
Climate Control
Sound deadening (not all of it!)
Heat reflective windscreen
ABS,ESP Traction Control
Boot Net
Mats
Later 172s also came with Cruise Control with speed limiter.
The Cup originally came in one Colour, Mondial Blue. Towards the end of the production run, it was also offered in Iceburg Silver.
The Cup has several suspension tweaks including stiffer springs, damping rates and as a result is slighlty (3mm) lower. Also, the Cup came with lightweight Speedline Turini alloy wheels with a different offset giving it a slightly wider track.
In adition, the Cup came with a small front splitter and enlarged rear spoiler, to increase the aesthetic appeal.
Thats about all I know, off the top of my head. Im not going to quote stats because that is another can of worms. The Cup is faster on paper by a few tenths to 60 and just shy of a second to the 100. The handling of the Cup is also better than the 172. On the road however, there is little difference (couldnt help chucking in my opinion, sorry).
If Ive missed anything Im sure someone will add to it.....