Recs.
Updated
SpecsUpdate
Pros
Pro Intelligent code completion
This feature is extremely helpful in projects where time is not a luxury that you have. Webstorm will auto complete JS variables, keywords, methods, functions and parameters. Not only that, Webstorm can also offer completion from methods and functions that are in any external libraries or frameworks.
Pro Code refactoring support
In today's day and age it is important not only to write code that works, but also code that is maintainable in the future. To make sure your code can be easily maintained, you must first be sure to make it is clean and tidy. This is the part where WebStorm really helps you, it automatically refactors your code by performing on it functions such as extraction of variables, moving files, inline variable extraction etc. All these make sure your code is clean and safe.
Pro Integrated code quality tools
WebStorm comes bundled with JSHint, JSLint JavaScript linters. JSCS, ESLint as well as Closure Linter can be installed via npm. They register as inspections and are customizable through IDE settings. They run automatically and will highlight potential issues. Pressing alt+enter on an issue will allow viewing suggested fixes.
Pro Reduces the amount of repetitive code that has to be written with code snippets
WebStorm includes a feature called Live Templates. Live Templates are predefined code snippets that can include variables. They're intended to increase productivity by reducing the amount of repetitive code that has to be written.
Pro Ability to base hot keys on previously used IDEs
When you install WebStorm, it allows you to choose from other IDE's for it to base it's hot keys on. So if you are switching from another IDE it makes it a very easy transition and productivity is not adversely affected by having to learn new hot keys.
Pro Interactive theme (color scheme) editor
Makes adjusting an existing or creating new themes a breeze. Especially due to things like inheritance, as well as easily exporting/distributing/importing the color settings which really only store where on deviates from the defaults (thus the resulting files are very small and relatively human-readable).
Cons
Con Not free for commercial use
A paid license is required to use WebStorm for commercial use. The license terms have changed (Nov 2015) and now require a subscription (per year: $59 personal, $129 for companies). Students can obtain a free non-commercial, educational license good for 1 year.
Con Slow performance occasionally
WebStorm can sometimes choke all cores of the CPU. There are numerous reports of high CPU usage.
Con Poor usability on option and menu navigation
You need to press a combination of keys or navigate through different menu levels to carry out the two most common things a developer does. For example, to run your code, the default is Shift+F10. To go to definition, you need to click on "Navigation" first. There is no sense to this: being forced to press a combination of keys hundreds of times or navigating through different menus can be a waste of time.
Con Occasional slow performance
WebStorm can sometimes choke all cores of the CPU. There are numerous reports of high CPU usage.
Con Constantly trailing behind on support for its main features
The Jetbrains team do an admirable job attempting to keep up with support for the features they wrap, but they are running an un-winnable race. For example, WebStorm 11.0.2 hangs when trying to debug NodeJS 5.0+ projects (30+ seconds before hitting breakpoint). By the time they fix it, 5.1 will be out and something else will break.
Con Non-native filesystem causes issues
The Java wrapper around the filesystem doesn't actively watch for file changes (by, for example, using the fsevents api on OS X), and as a result can become easily desynchronised from the actual filesystem.
If you have an external tool acting on your project (such as a gulp task or a third-party Git client), what you see in the file browser or in open tabs becomes out-of-date. There's a feature in the context-menu for manually synchronising directories with their real filesystem equivalent, but this shouldn't be necessary and is annoying to do. You usually remember to do that anyway after you've been trying to track down a bug on a line of JavaScript that Webstorm says doesn't exist for the last two hours.
It should be noted though that this is easily remedied by going to File/Settings/System Settings and checking the "Synchronize Files on frame or editor tab activation" option. It's also recommended to more explicitly represent your workflow within WebStorm itself. Most external tools/tasks can be handled with WebStorm. And if it's not in a plug-in, then you can handle it with the File Watchers.
Con Plug-in ecosystem isn't robust
Every framework or extension with any popularity whatsoever will have a plugin for VS Code. Sometimes they'll still support Atom. Only one in twenty will have native support for WebStorm.
If you want support for the latest libraries, you won't get it in WebStorm.
Recommendations
Comments
Flagged Pros + Cons
Pro Maintains a local history
The local history feature in Webstorm tracks all your local changes in the source code that you are making. You can use it to view changes that you've made to your code and roll back whenever necessary.