Several years ago, I started Atomizr as Ruby CLI that lets you convert Sublime Text completions/snippets into Atom snippets, and vice versa. Soon after, plug-ins for Sublime Text and Atom followed.
Only recently, I rewrote Atomizr in JavaScript, mainly because my upgrade to Sierra screwed up my Ruby environment.
Functionality | Ruby | Node | Atom | Sublime Text
-----------------------------------|------|------|------|-------------
Atom to Sublime Text | | ✓ | ✓ | ✓
Atom to TextMate | | ✓ | ✓ |
Atom to Visual Studio Code | | ✓ | ✓ | ✓
Sublime Text to Atom | ✓ | ✓ | ✓ | ✓
Sublime Text to TextMate | | ✓ | ✓ |
Sublime Text to Visual Studio Code | | ✓ | ✓ | ✓
TextMate to Atom | ✓ | ✓ | ✓ |
TextMate to Sublime Text | | ✓ | ✓ |
TextMate to Visual Studio Code | | ✓ | ✓ |
Visual Studio Code to Atom | | ✓ | ✓ | ✓
Visual Studio Code to Sublime Text | | ✓ | ✓ | ✓
Visual Studio Code to TextMate | | ✓ | ✓ |
Toggle Atom format | | ✓ | ✓ | ✓
Toggle Sublime Text format | | ✓ | ✓ | ✓
Batch conversion | ✓ | ✓ | |