Hi Annalisa:
Thank you for your question. Right now there are 3 main differences in user experience, and the team continue to work hard and unify the experiences.
1. Desktop client (preferred experience) - To join using this experience you can launch the meeting from the top of the Webex app, or on the website if you click the scroll down of the green button, you can make sure you are launching the Desktop client
2. Web client - This is a WebRTC client which has limited features
3. Webex space meeting - This is also a different experience, and it's used when you schedule a space meeting in the app, in the future this will be the same experience as the Desktop client
I hope this helps. Happy to talk live if you prefer or have additional questions.