Which Plugin Format for Logic X

TL;DR

When installing plugins for LogicPro X, only Audio Unit (AU) is needed.

Slate’s installer actually has awesome descriptions of various formats!

slate_plugin_formats_description

AAX Pro Tools plugin format, Pro Tools 10 (32 bit) and later (64 bit)
- RTAS is for older Pro Tools
AudioUnit is Apple’s plugin format, used in Logic, Studio One, Ableton Live and many more.
- This is what Audio Hijack uses as well.
VST [aka VST2] is Steinberg’s plugin format, used in Cubase, Studio One, Ableton Live, Reaper and many more.
- The original GOAT. Can be 32 or 64 bit, depending on the plugin.
VST3 is Steinberg’s new plugin format, used in Cubase, Studio One and Wavelab.
- Supported in Ableton Live 10 onwards.