French patio doors are extremely stylish. They give your home and patio a continental feel and establish a European sense of style in the decor of your house. This will be extremely impressive to your friends and family, and it can be accomplished without a large monetary investment on your part.
French patio doors make it easy to move between the interior and exterior of your home. This is especially true when you are carrying a tray full of food from the kitchen to the deck. French patio doors are more cost effective than sliding glass doors, and they do not have the same dangers associated with them. For example, children can sometimes mistake a closed glass door for an open doorway, and will run right into it, thus sustaining injuries, sometimes of a dangerous or life threatening sort. This kind of thing would not happen with French patio doors because French patio doors are opaque and easy to see.
Interior french doors are similarly stylish and sophisticated. They also offer privacy from room to room while at the same time allowing for the easy accessibility you cannot have with a solid door. I would not, however, recommend making your bedroom door into French doors, because you need to have more privacy in that room than in any other in your house.