IMO, the most important features are:
* Analog gain (most important, and separate L/R control is GREAT) - of course, with AGC off
* Digital gain set to zero (for cleanest audio)
* Input source (internal mic, external mic, or combinations like Left internal, right external, differential)
* Audio monitoring (when you plug the A/V cable, keep audio signal on the A/V jack, but keep the image on main display)
Sure, it may be nice to have equalizer presets, but as long as you have the cleanest raw signal (without digital gain / filters), you can apply any filter in post.
Big up for Coutts - the datasheet is very well written.