I usually do the shopping for the week on Sundays, and I often leave the meat in the refrigerator for 5 or 6 days, so I am wondering if it would be better to freeze it immediately after buying it and defrost it later or just keep it in the refrigerator.
This depends on the type of meat. Poultry, ground meat, and offal should only be kept at refrigeration temps a couple of days, so you probably want to use first or freeze. Steaks, chops, and roasts can hang around in the refrigerator a few days more. By day 6, you are getting near the end of the window, so it might be better to freeze. Personally, for all cuts, if I am not using in the next two days, I freeze. Simply because life gets in the way...or plans change, and I may not use the product when I think I am going to. So, you can't go wrong by freezing, as long as you build defrosting into your weekly plan. In this case, I move from freezer to fridge one or two days in advance.