Standard v standard...
The mk2 172 is fractionally quicker to both 60 & 100 than the Cupra R, but theyre very close. The mk1 is a shade quicker again, then the Cup again slightly quicker than that, so in a drag style race, the Clio(s) would always be just in front.
However, the Seat (having a turbo) has a lot more torque than the Clio with 199lb/ft (compared to Clios 147lb/ft), which peaks at an amazingly low 2100rpm (compared to Clios 5400rpm) and a great big fat band of torque throughout the rev range. So mid range and in gear flexibility are huge on the Seat which will just pull like a train in any gear at any speed.
Modifying...
The Seat has the VW/Audi 1.8 20v turbo engine in there, so tuning potential is huge and you can get a hell of a lot of power (reilaibly) from that unit, so there is the makings of a very quick car!
A lot harder to get massive power out of the 172 engine, so without spending the debt of a small African country then youre not gonna see the same sort of power gains.
Simple fact is that turbod motors are easy to tune.
A guy at my work has a red one and it does look hard as nails in the flesh and so much better than in the mags. My mate at work with a CTR was saying hed probably go for a Leon next.
Pound vs performance as standard though and the Cup is the clear winner.