hyperref vs hyperxmp

The two packages differ heavily so there is no «better» or «worse».

1. The bigger and older and more low level hyperref mainly is about creating links in PDF. It can also add some metadata that are Document Info, not XMP. But the former are more and more being replaced by XMP metadata.
2. The smaller and newer and more high level hyperxmp does not interfere with links. It mainly adds XMP metadata to the PDF. hyperxmp is built on top of hyperref. hyperxmp can use the interface of hyperref: hypersetup{pdftitle=mytitle} will additionally create an XMP entry called dc:title when you usepackage{hyperxmp}.
   But hyperxmp will also do some higher level stuff. When you just say Title{mytitle} in a document hyperxmp (if loaded) will translate this to hypersetup{pdftitle=mytitle} thus leading to a Document Info and XMP metadata. The newest version will even load hyperref if you don't to it yourself.