Today I am using XMLBeans, but we are interested to move to JAXB. But I don't know if I can do everything that we do with XMLBeans. For example, how can I use "choice" in JAXB, or validate the "in parameters" automatically before the webservice method execute. Somebody had some similar experience with both? What is better?
Yes, you can do validation of XML documents against XML schema using JAXB.
If you want to know whether JAXB can cope with some XML schema you have, then I would suggest using XJC (the JAXB schema compiler) to generate JAXB Java classes for the schema.
Then you can examine the generated classes and see if they are appropriate for your needs.