benefit or drawback to define plant at sales organization level

at the time of creation of sales organization i have define plant at sales organization level.

there is another setup in IMG and that is "Assign sales organization - Distribution Channel - Plant".

what is the purpose of plant at sales organization level and what impact will occure if i assign plant on sales organization -distribution channel - Plant level. ?

kindly assit me that what will be better should i define plant at the time of creation sales organization of should i use IMG setup "Assign sales organization - Distribution Channel - Plant". ?