When I first started working in Illustrator, Outline mode (Artwork mode) was the only way to work on a file. No work could be done in Preview, which was just for looking at, and hopefully admiring the art. This was not easy, and could be quite frustrating at times. Flash forward about eight versions and working in Preview mode is so old many users have forgotten (or never knew) about the advantages of working in Outline. Advantages? What advantages?
If you’re working on a complex image with lots of Blends, Effects, Patterns, and Placed Images, everything can grind to a halt while waiting for your screen to redraw. This is especially true using older computers. To speed up your work, switch to Outline mode (View > Outline) and avoid the drawn out redraw process. The other big advantage of Outline mode is that it gets all those beautiful Fills, Strokes, Blends, and Placed Images out of the way, so you can select whatever is hidden behind them. Quite efficient!
Tip provided by Jeff Witchel, Certified Adobe® Training Provider.