Which text editor has better OSX support, TextMate, or Sublime Text 2
Go with what you're familiar with and don't worry about whether you're missing something or not.

Familiarity will trump any additional features you might likely discover in TextMate and the ability to sit in a familiar coding environment no matter what OS you're working is a really big productivity boost.

Overall Sublime Text 2 is a move forward from TextMate at the time I'm writing this. It has better undo semantics. It can load in most TextMate bundles so you can extend it in the same ways TextMate can be extended. Though, truthfully, after switching from TextMate this year I haven't found a need to install any TextMate bundles because anything I had been using in TextMate was available as a better implemented, more feature rich bundle in native Sublime Text 2 format so far.

This being said, TextMate 2 is in alpha and can be downloaded, so an update is on the distant horizon. But my advice still stands: familiarity on multiple OSes is a fantastic thing for your development environment.