This is a question that arises often because both of these types of patio door are very popular, but both function in very different ways. Here are some typical features of each to help those who are in the process of deciding which suits them best.
OPENING FUNCTION: French doors open outwards – Sliding doors move sideways within the frame.
CLEAR OPENING SPACE: French doors open wide (90 degrees or more) to give a clear opening – Sliding doors overlap and restrict the clear opening space.
VISUAL APPEARANCE: French doors offer many classic design features to make them interesting – Sliding doors are usually 100% plain glass.
FLEXIBILITY: French doors are a matched pair of 2 doors, so for larger openings, you have to fit fixed side panels – Sliding doors can deal with any size opening
ENERGY EFFICIENCY – both can be very energy efficient
In summary, if you want a patio door that has some character and looks timeless go for French Doors – if you have a larger opening and want a slimline, uncluttered appearance go for sliding doors.