“ a decal is a more professional word for sticker”… No; 
“ I would think of a sticker as say a white label and a decal as clear”… No; 
“ Usually a sticker is paper, example an Avery label and not durable and a decal has a permanent adhesive and is more durable”…  No, no, no!

What I understand these words are used interchangeably among people. But according to the experts a decal is basically a decorative sticker, generally used OUTDOORS.

They can be rather easily transferred from one surface to another and will have three layers: transport paper on the back, the decal itself, and a mounting film on the front. A sticker is generally more basic and has two layers: the decorative layer which has adhesive on the back side and pattern on the front; and the transport paper on the back which you peel off. Stickers are adhered, not easily transferable. 

Decals are often made of a vinyl and die-cut. Basic stickers are often made of plastic and have a background, either transparent or colour.

Basically what this all means is that yes, there is a technical difference based on the dictionary definition of each term, but so few people understand the difference it’s meaningless All you need to know is that whether it is a sticker or a decal, Speedpro can make it for you. 

-Speedpro Imaging Halifax