Start by copying/replicating designs from dribbble. It's just practice. After you learn how to use Photoshop/Sketch start modifying those designs and try to make it your own.
My biggest benefit is working with multiple artboards. As we all know, design now starts with going mobile first. Right from the start there is a mobile view, tablet view, and desktop view.
Other pros
+ Text Styles (Save a font style for h1,h2,h3,p. Why hasn't anybody else done this?)
+ Better color picker because it magnifies to the pixel. Much easier/faster to find colors on text.
+ There's like 10 colors on your active palette. Photoshop is 2.
+ Faster to export images.
+ Duplicate/Copy anything faster than Photoshop.
+ Opens up way faster than Photoshop. Similar to opening a text editor.