Differences between Elementor Addons for Posts Widget
Let’s see how the Elementor Addons differ from each other with regards to the Posts widget.
Basically there are three main settings for the Posts widget: Layout Settings, Query Settings and Styling Options.
Posts Widget Layout Settings

First of all, there is a difference between the addons in available skins (1) that you can use to showcase your posts. The Ultimate Addons for Elementor* offers six different skins, and you can add even more to your Elementor site.
From my perspective, another important thing about the layout is the ability to set a custom image size (2). I don’t really understand why this is not available in the out-of-the-box Posts Widget from Elementor Pro. This setting is essential if you want to optimize the GTmetrix audit for Properly Sized Images (former GTmetrix audit: Serve Scaled Images). With Ultimate Addons or Premium Addons for Elementor*, you can use the custom size of your images.
Posts Widget Query Settings

As you can see from the screenshot above, there are differences about what post types you can include in the query (1). While Ultimate Addons and JetElements allow to include Custom Post Types, this is impossible with the Posts Widget from Elementor Pro. If you want to extend the query setting, you can also include custom queries (2). With Ultimate Addons and JetElements, you can do this within the Elementor Editor, whereas with Elementor Pro, you need to write your custom query in the functions.php of your Child Theme and include the Query ID.
Posts Widget Styling Settings

The same applies to the styling settings of the Posts Widget – for instance, there are much more customization options available for Ultimate Addons and JetElements than for Elementor Pro.