how big is "big whitewater"???
Its a hard one i suppose because your wanting to take part in a few disciplines. A river runner/mild creeker shouldnt be to much of a problem. I dont think id do any sort of serious creeks in an allrounder though, depends on how big they are.
In the UK there isnt anything like the amount of volume and big rivers there is in the states. I mean im no expert on creeking(or paddling in general) and i cant say ive done any really big rivers but ive done rivers that are so low it was basically a rock bashing trip and i was glad i wasnt in my own boat because i wouldnt want to do anything like that in a playboat or an allrounder to be honest.
I now have a playboat but i used to paddle an allrounder. Obviously the allrounder does what it says on the tin but what it dosent say is that you A)probably wont become a world freestyle champ! and

Ull probably smash it to smithereens if you try a 200ft drop in it!
As far as surfing an allrounder goes, ive done it but its not easy if you want to do more than go in a straight line.
So:
big creeks = creeker
Bit of everything = allrounder
more surfing than anything else = get a surf yak.
Saying that i spoke to a guy the other week who does whitewater, playboating and surfs all in a fluid element.
still confused? I know iam???
matt