I use the miniblinds with a UV resistant marker (mine is called "garden marker"). I find pencil too light and hard to read from a distance. I use the miniblind markers for pots of plants that sell within a year or two. For garden plants I use 4X5" steel garden markers with an 18" stake. I print laminated cards for the label that fit in the steel holder. They last about 10 years and then the cards need replacing. I just use them for plants that are unusual or rare and it is great when people tour the garden and can read the history and other information about the plant. I usually put where the plant is from, date it was planted, Zone, and other unusual features like color, Height, Deer resistance, and uses.
I don't use plastic label holders because I destroy them when I weed whack...