Difference between two ways of embedding metadata into pdf outpurt [duplicate]

Question

The following source, using hyperref, shows two different ways of embedding metadata into the output from using pdflatex:

1. Using the pdfx package with option a-2u — this happens when the flag validate is set to true, as it is below.
2. Using instead the hyperxmp package with \hyperrefset including options pdfapart=2, pdfaconformance=u — this happens if the flag validate is set to 'false`.

Both methods seem to embed essentially the same metadata about title, author, etc., into the pdf.

Questions:

• Aside from passing PDF/A-2U validation (which method 1 allows but method 2 does not), in fact is there any actual difference in the embedded metadata?
• Is there some reason to prefer one method to the other (aside the issue PDF/A-2U validation)?

Source:

\RequirePackage{filecontents}

\begin{filecontents}{\jobname metadata.xmp}
\hyxmp@at@end{%
  % Create XMP code and write it to macro \hyxmp@xml
  % (cf. hyperxmp.sty, \hyxmp@construct@packet (ll. 847-868))
  \gdef\hyxmp@xml{}%
  \hyxmp@add@to@xml{%
<x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="3.1-702">^^J%
___<rdf:RDF
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns\hyxmp@hash">^^J%
  }%
  \hyxmp@pdf@schema
  \hyxmp@xmpRights@schema
  \hyxmp@dc@schema
  \hyxmp@photoshop@schema
  \hyxmp@photometa@schema
  \hyxmp@xmp@basic@schema
  \hyxmp@mm@schema
  \hyxmp@add@to@xml{%
___</rdf:RDF>^^J%
</x:xmpmeta>^^J%
  }%
}
\end{filecontents}

\begin{filecontents}{\jobname.xmpdata}
\Title{A Book}
\Author{Anonymous}
\Language{en-US}
\Keywords{things\sep stuff}
\Subject{matters}
\Publisher{Anonymous}
\Copyright{\copyright 2020 The Company CC-BY-NC-ND}
\CopyrightURL{https://creativecommons.org/licenses/by-nc-nd/4.0/}
\PublicationType{book}
\Lastpage{3}
\Date{2020-06-26}
\CoverDisplayDate{June\ 26,\ 2020}
\CoverDate{2020-06-26}
\end{filecontents}

\documentclass{book}

\usepackage{ifthen}
\newboolean{validate}
\setboolean{validate}{true}  

\ifthenelse{\boolean{validate}}%
  {\RequirePackage[a-2u]{pdfx}%
    \pdfglyphtounicode{EM}{0058 0058 0058 0058 0058 0058 0058 0058}%
    \pdfglyphtounicode{NUL}{0060 0060 0060 0060 0060 0060 0060 0060}%
    \RequirePackage[type={CC},modifier={by-nc-nd},version={4.0},lang={english}]{doclicense}
    \usepackage{hyperref}
    \hypersetup{
       pdfa,
       bookmarksnumbered,
       pdftitle={A Book}, pdfauthor={Anonymous}, pdfcreator={somebody},
       pdfsubject={A general introducton to things}, pdfkeywords={things, stuff},
   }  %  
}%
  {\RequirePackage{hyperxmp} % to add CC info into pdf
   \RequirePackage[type={CC},modifier={by-nc-nd},version={4.0},lang={english}]{doclicense}
   \usepackage[pdfa]{hyperref}
   \hypersetup{
      pdfapart=2, pdfaconformance=u,
      bookmarksnumbered,
      pdftitle={A Book}, pdfauthor={Anonymous}, pdfcreator={somebody},
      pdfsubject={A general introducton to things}, pdfkeywords={things, stuff},
      pdflicenseurl={http://creativecommons.org/licenses/by-nc-nd/4.0/}
    }%
    \immediate\pdfobj stream attr{/N 3} file{sRGB.icc}
    \pdfcatalog{%
        /OutputIntents [
           <<
             /Type /OutputIntent
             /S /GTS_PDFA2
             /DestOutputProfile \the\pdflastobj\space 0 R
             /OutputConditionIdentifier (sRGB)
             /Info (sRGB)
          >>
      ]
    }
}

\newcommand\mytitle{A Book}
\newcommand\myauthor{Anonymous}
\newcommand\myabstract{An introduction to things in general.}
\newcommand\mydate{\today}
\title{\mytitle}
\author{\myauthor}
\date{\mydate}

\usepackage{newtxtext,newtxmath}
\usepackage[french,ngerman,russian,main=english]{babel}

\usepackage{blindtext}

\begin{document}
\maketitle
\blindmathpaper
\end{document}

Related:

Validate pdf with and without pdfx

pdfx + hyperref prevents setting PDF metadata [incompatible packages]

Is it possible to use both hyperxmp and xmpincl in LaTeX?