I think it would depend on whether both doors open and whether you use both doors. Myself it's almost like having a patio door...except that the doors open rather than slide. I have vertical blinds on my patio door but they are not great for keeping out the cold. If you have room on both sides of the doors for drapes to hang, I'd probably put drapes on a rod that is long enough that you can draw back away from the doors when you want the light or to use the doors. Then you can draw them closed at night when you want to keep the cold out.
These are some ideas that I found. I kind of like the one hanging from the rings...but it's not really practical for being able to use the door, IMO.
http://www.bhg.com/decorating/window-treatments/basics/window-treatments-for-sliding--french-doors/#page=4They also have rods that you can swing the curtains back from the doors...but you'd probably see the wrong side when they are swung back away from the doors.
Being from the cold north...I have insulated drapes in my living room. I've had them for years...bought them when I was in an apartment that had old windows. The drapes are 144" (12 ft) wide and are on drapery hooks that slide across a 10 ft rod and extend well past my 6 ft wide window. I open them wide in the daytime and draw closed at night. They really help to keep the cold out on the long winter nights.
Edited: Just thinking of when I bought them...
back in 1987...and what I paid for them...a 50% off clearance bin and they still cost me $144. But I've had them for...25 years. Egads...I guess I got my money's worth.
And it shows that I don't redecorate much...