Hello Worldfoot, thank you very much for contacting us.
To answer your question, as per AHCI performance or functionality there was no change and possibly you didn't lose anything by doing the downgrade.
Driver updates usually involve fixes for glitches found previously but it doesn't mean that an older driver version is bad.
In your particular case it looks like Crucial identified problems with the current AHCI driver version; reason why they recommended doing that, but possibly due to manufacturing or design matters with your laptop, the older driver is working better for you.