What are the differences between MS and UC headsets? 

MS - Optimized for Microsoft Team or Skype For Business (SFB)

UC - Unified Communications (Generic)

Essentially, the basic functionality of the headset will work the same. 

The Microsoft (MS) variants, which are certified for use with Microsoft Teams, support a plug-and-play experience with the following features:

• The automatic selection of the MS variant as the default communication device.
• Microsoft Teams LED notifications that are visible on the Jabra device.
• A dedicated Microsoft Teams button on the Jabra device that supports interaction between the device and Microsoft Teams on a computer.
• If multiple MS devices are present, call prioritisation will send the audio to the device that was used to answer an incoming call.

If you use an MS variant with a different softphone client, the MS variant should work the same as a UC variant does with regard to audio and standard features such as answer/end calls, adjust volume, and mute microphone.

If you do not use Microsoft Teams as your softphone client, we recommend you use a UC variant, which is certified for use with all leading UC platforms including Cisco, Mitel, and Avaya. If you use a UC variant with Microsoft Teams, the plug-and-play experience will not be available. You can set up audio and call control features manually by selecting the UC variant as the default communication device in the Microsoft Teams settings.

MS Certified Phones and Devices for Microsoft Teams - Microsoft Teams | Microsoft Docs

Certified devices

Table Updated March 2021