Lync URI vs SIP URI

[MdotQ]

Does anyone know why some sites(free) send out Lync URI for skype for business and others give the format <meeting number>@webex.com to dial in with skype in the invitation email ? 1st is one for paid users(Left one), 2nd one is for free users
Just curious to know the reason behind this format

[Ashish Patel · Accepted solution]

We have standardised on one way to join into the meeting regardless of where the calling party is coming from now. Webex will work out what to do. So one address to call only.
https://help.webex.com/en-us/nrzuwjt/Start-or-Join-a-Cisco-Webex-Meetings-Video-Meeting-Using-Skype-for-Business

So invite will say now say
Join by video system, application or Skype for business
Dial 1111111111@webex.com