The benefits of having a door blind are many. For example, if you have a large amount of glass on your door, this is a weak point in your home, not only as far as security is concerned, but also for the weather. A door with a big glass pane will suck all of the heat out of your home during winter, increasing your electricity bill as you try and keep the house warm.
The first thing you need to ask yourself is what type of door you need a blind for. Some doors have glass panels in the top half, and the most popular blind to use in these situations are venetians. Some people refer to these blinds as mini blinds, but the meaning is the same. These are blinds that have slats that go horizontally along your glass. These blinds are operated via cords that run down the left or right side, allowing you to tilt the shutters backwards and forwards and limit the amount of light that comes through.
There is another type of blind that can be used on these doors, and it is the roller blind. The problem with roller door blinds is that you are limited to the amount of light you let in. Unlike the filtering effect you can achieve from venetians, roller blinds only give you the option of having the blind open or closed. In some cases this may be all you need, but the benefit you get from having mini blinds is well worth the little bit extra that it will cost. If you want your blind to look more stylish, you may want to consider getting wood blinds (or faux blinds, if wood is above your price range).
For your larger doors, like the patio sliding doors, a vertical blind is the way to go. When you have a larger door to cover, you have the added benefit of being able to use larger slats on your blind, which, in my opinion, gives you a much better look for your money. Vertical blinds are great, because they tuck into the corner when not in use, allowing you to get the full benefit of the view out of your big glass sliding door.