It depends on the protein source. If its a whole food with high fat content is will easily slow digestion but if its powders then they will be processed at a faster rate (although somewaht different depedning on source)
If you are eating a meal then a good lean source of slow protein is good pre-workout then post workout you DEFINETLY want a fast source (whey).
If you pre workout meal consists of a shake then a good whey/casein mix would be good.
There are just a lot of variables to take into account.