The difference between reCAPTCHA v2 and v3 is in the way they work and the user experience they provide.
reCAPTCHA v2, also known as "No CAPTCHA reCAPTCHA", presents the user with a checkbox to confirm that they are human. This version can also include a challenge where the user has to identify and select specific objects in an image.
reCAPTCHA v3, on the other hand, runs a risk analysis in the background and assigns a score to each interaction with the website. Based on this score, the website can then choose to either let the user pass or present them with additional challenges. With reCAPTCHA v3, the user doesn't need to solve any challenges or complete any specific actions - the risk analysis is performed in the background and the user experience is much smoother.
In terms of which one is better, it depends on the specific needs of the website. reCAPTCHA v3 is more user-friendly and less intrusive, but it may not be as secure as reCAPTCHA v2, which provides a more direct challenge to the user. It ultimately depends on the security level required and the desired user experience.