The main difference between Blended Scotch and Single Malt Scotch comes from their ingredients.
Single Malt Scotches can only be made with 100% malted barley while Blended scotch is a mix of Single Grain Whisky and various single malt whiskies.
Blended scotch tends to have a more consistent flavor profile. Offering a wider range of flavor notes but less pronounced/distinct regional characteristics.
Single Malt scotch showcases the unique qualities/tastes of the distillery and/or region.