Have never really thought about this, but after seeing the title of this thread it prompted me, and oddly enough I think I would keep my Cup.
I'm not disputing the Trophy's superb attributes in the slightest, but I love the raw edge of my Cup. Got to have been one of the last cars built without ABS and various other electronic aids (ignoring TVR etc), so no matter how advanced things get from here on in the Cup will always be one of (if not the) last car from a major manufacturer to be relentless in its pursuit of weight loss and driving experience.
If it was a case of "here's £14k, buy a Clio" though, I would get a mint 172 Cup for £8k or so and spend a few grand on it, coilovers, ITG Maxogen, Recaros, exhaust, 4 pots. Could have one hell of a car after that sort of work!