Evan Solomon

<a href="http://oembed.com/" rel="nofollow ugc">oEmbed</a> is an easy way to embed media. It turns links into embedded content automatically. WordPress has supported it in posts for a while, but not in comments. This plugin uses the oEmbed support already in WordPress and adds it to comments.

oEmbed in Comments

still works

WordPress supports oEmbed, but only in post content. This adds oEmbed support to comments.

Embedly

Enhance the default WordPress embedding to get previews for any article, 
including your own blog posts. You also get embeds for YouTube, Vimeo, Twitch, 
Google Maps, and Embedly’s growing list of <a href="https://embed.ly/providers" rel="nofollow ugc">1000+ supported 
providers</a>.
You can customize the style of the embeds, to optimize for darker WP themes, 
alignment, and width. In addition, social buttons can be added around the embeds 
to make it easier to share content from your blog posts.
If you have an Embedly Cards account, you can link it to the plugin with your Embedly API key. Not only does this remove branding from the cards, it also gives you access to analytics and viewer behaviors for most popular music and video player embeds (YouTube, Vimeo, Instagram, SoundCloud). Find out how many people viewed your embeds for how long. To learn more about Embedly Cards please visit <a href="https://embed.ly/cards" rel="nofollow ugc">our website</a>.
Using it is as simple as the default WordPress embedding. Embed media by pasting its URL in a single line when writing a post.
The plugin automatically displays an embed of the media in the WordPress post editor.
Fair Warning: This plugin generates static HTML content for your posts. After you deactivate 
the plugin, that HTML will still remain behind in all posts where the plugin was used to create 
embeds.

The Embedly Plugin extends WordPress's auto-embed feature to give your blog more media types and style options.

oEmbed in Comments vs Embedly