I switched from the API channel to the SSL because I found the SSL did a better job of permitting the color of my microphone come through, with minimal additional coloration of its own. The compressor is also more pleasing to my ears, contributing energy without calling unwanted attention to itself.
The expander is a disappointment, though. The lowest threshold it allows is -30 dB, and both the compressor and expander lack attack, ratio, and knee controls. I understand the plugin is intended to emulate, as closely as possible, the hardware unit it's modeled on. I'm saying that, precisely because of those constraints, for my use case (recording audiobook narration), the expander is useless.