PhpStorm has two types of autocompletion: structural completion and word expansion. Structural autocompletion makes predictions based on its understanding of PHP, while the latter tries to predict the word currently being typed based on previously typed words. Word expansion also works in comments...
Atom is not a native application. As such performance is subpar and the lag is especially noticeable on larger projects. It also opens a surprising amount of sub-processes and leaks a considerable amount of memory.
Since Version Control features are very frequently used these days, having them built right into your IDE seems quite the right thing to do. With Komodo, you can perform your Git push-es and pull-s right while you're coding.
Aptana has a couple of dependencies to keep in mind. It is built with Java and and has some requirements for the JDK version. Aptana requires Git, and Eclipse 3.5+ if you are installing it as an Eclipse plugin.
Vimscript provides a rich scripting functionality to build upon the core of vim. When combined with things like Tim Pope's Pathogen plugin management system, it becomes easy to add support for syntax, debugging, build systems, git, and more.