In reply to Robert Durran:
I'm not sure it was Arms who missed the point. The comparison is of 9a onsight with bold E10 (or E9 if talking about IF)
You can indeed play the percentages game but that doesn't mean you have a hope in hell of winning it. Even if the best sport climbers in Britain blow the 9a onsight 99 times they will still have effectively zero chance of getting up the next one. Just because they won't die trying doesn't mean success is a genuine possibility.
If the best bold trad climbers in Britain took an interest in trying IF onsight effectively all of them would say 'no thanks, not today', which equates to a similarly negligible success rate. You don't need to fall and die in order to have not succeeded.
However, a day will come when a British super-talented bold onsight climber will decide that trying IF onsight is within his/her capability and acually try it. They may get high and back off but sooner or later one will commit to the crux, in which case it's likely they will succeed (how many people have fallen from cutting-edge chop routes?).
A day will also come when a British sport climber is good enough to onsight 9a and actually succeeds in doing so.
My guess is that day of the former will come before the day of the latter.
ps. I've kept it to talk of British climbers as I believe the top levels being climbed by Brits at present in trad and sport are roughly comparable. IF is one E grade above today's top level, whereas 9a is 3 sport grades (1.5 E grades?) above today's top level. Ondra is streets ahead.
pps. I'm sure The Cad (E6, equating in overall comparative difficulty to sport 7c) has been onsighted by people who have never even come close to being able to onsight 7c. There's also pleanty of people who've onsighted 7c who wouldn't want to go near The Cad onsight. Horses for courses, yes, but that's what the E grade compares and does so very effectively on the whole