Komodo's auto-completion feature is excellent, similar to the one found in Microsoft Visual Studio: You get a scrollable menu with completion options, rather than having to blindly tab between options. I compared it with jEdit, editing a simple snippet of CSS, and it fared significantly better; jEdit's auto-completion stopped working after a few attempts. Komodo Edit also features other amenities, such as code folding and simple text zooming using the mouse wheel.
If you already know you need a full-fledged IDE, choosing between Komodo IDE and competitor JetBrains PhpStorm is a tough call. But if you're not sure whether you need an IDE or just a powerful editor, you can start out with free Komodo Edit and maybe graduate up to IDE if you find you need advanced features such as debugging or source code control integration.