When I first started implementing structured data markup into this site. I had the option of going with JSON-LD or Microdata formats. Microdata was the clear winner for me, but that may not prove to be the best choice. The main reason I went with the microdata format was that I believe it didn't require duplication of data like the JSON-LD format does. I don't know how you could implement JSON-LD without the duplication of data or without using a JavaScript function to populate visible content on a page. Here is a quick example of the two.
Microdata Example
<ol itemprop="breadcrumb" itemscope itemtype="https://schema.org/BreadcrumbList">
<li itemprop="itemListElement" itemscope itemtype="https://schema.org/ListItem"><a itemtype="http://schema.org/Thing" itemprop="item" href="https://www.bryan-myers.com" title="Home"><span itemprop="name">Home</span></a><meta itemprop="position" content="1"></li>
</ol>
The displayed content for this breadcrumb example is the EXACT same data used for the structured data.
JSON-LD Example
<ol>
<li><a href="https://www.bryan-myers.com" title="Home"><span>Home</span></a></li>
</ol>
<script type="application/ld+json">
{
"@context": "http://schema.org",
"@type": "BreadcrumbList",
"itemListElement": [{
"@type": "ListItem",
"position": 1,
"name": "Home",
"item": "https://www.bryan-myers.com"
}]
}
</script>
The data is listed TWICE. Once for the displayed HTML content and again for the JSON-LD object.
I think I am going to try two things in the near future. The first is going to be implementing BOTH microdata markup and the JSON-LD objects. Since my object data is dynamic, this should be a pretty easy addition. By adding the JSON-LD objects to the end of the page using the same query data, there shouldn't be any problem with mismatched data values. If the results from that test appear to negative effect on my SERPs listings, I will try dropping down to just using the JSON-LD implementation. Either way, it should be an interesting experiment.