Isn't he talking about CF in that post? Not audit market share of the FTSE 100? From what I know (granted hearsay so may be completely off base); KPMG lead CF, PWC lead audit, Deloitte lead consulting and E&Y look pretty.
Anyway, you both sound a bit childlike to be honest (even though the other poster will be an old man by now). 'My firms better', 'no my firms better'. They're all the same thing in a different wrapper, let's be honest about it. Unless you work for E&Y that is, they clearly suck (joking!).
Anyway, long story short I recognise you're excited about your offer (congrats btw!), but try and fix that attitude of "9 years in a row at number 1... PWC is clearly the best". It shouldn't escape notice that the big 4 rank in roughly the order of the number of graduates they recruit on the Times list (or at least when I was looking), complete shocker given the way the list is formulated. Anyway the list needs to be taken with a pinch of salt, for example if you believe PWC is a bigger land than say Goldman or McKinsey then you're clearly mistaken.
All that said, I'm sure you'll have a great time (although not from Jan '14 - March '14, that's going to suck
). Good luck!