the rugby codes are different in the type of fitness required.
Aussie rules you need to be able to sprint repeatedly.
Rugby players get a lot more time to recover and they hardly ever make any big runs, its all in close contact.
To establish the stamina base reaquired for aussie rules will always detract from the power aspect, but like smokey, i dont believe there would be too many 100kg plus blokes quicker than AFL midfielders all the same.
I think the big difference between the types of fitness required is shown in that rugby players can back up and play 3-4 days later, probably not at 100%, but AFL players would really struggle to do that at all.