Sir,
The ip web-cache redirect in command is only a new addition in the late 12.1 and 12.2 train of IOS. Both commands do the same thing except the redirect in is on the interface where client sourced traffic enters the router and the redirect out is on the interface interface of the router. You do no use both at the same time.
My preference is for redirect in as the router does not need to route the packet because wccp picks the packet up on the incomming interface.
Cheers
Phil