In short and in an idle moment I tried both. I took sets of five shots with IS in body then same subject and same exposure details with IS in lens instead. I did this at full zoom only, but tried targets ranging from 200 yards to several miles.
I won't bore you with the shots (in fact I've already deleted them!) but they came down in favour of IS in camera. There was a slight but consistent performance advantage done this way (shutter speed was 1/125th throughout).
However, there's a rub: I found that there's less shutter lag when doing IS in lens.
You pays your money and you takes your chance...
Hope that helps someone!