What is the difference?
Nice such a new version, but what are the implications for you? Through machine-learning, among other things, you will get better insights into customer-journey of your website visitors. The data is going to help you get better insights, which are displayed more clearly. For example, in the current UA version there are more than 150 reports from which you can extract data, this has been reduced to about 30. This gives you more overview on the one hand, and on the other hand the figures are better displayed through visual aspects.
Do you also have an app or web application? Then the new GA4 version gives you many more insights. Previously you had to set up your own Analytics for each platform, now all data is collected in one property and you can better analyze where the traffic comes from with the best customer journeys for your product and/or service.