It´s not even comparable to begin with and this is a common misconception around Oxygen.
Elementor is a page builder not like Oxygen...Oxygen is a THEME BUILDER!
Big difference!
In fact, the first thing you will notice when installing Oxygen on your WordPress is that all active themes you have will become disabled by default.
So, using Oxygen will be the closest you´ll ever be to build a custom-made theme from scratch without having to write thousands of lines of code nor having to worry too much about performance since the only code injected into the site will be the one generated by Oxygen.
Oxygen started as a tool built by web developers for web developers but over the years they have made great improvements to its UI to make it more user-friendly so anybody without a web development background can use it.
But, as stated above, Oxygen still requires you to understand and/or have working knowledge on HTML and CSS to get the most out of the tool but, again, this is something that can easily be achieved by watching one of many great tutorials on YouTube on these topics.
It shouldn´t take you than a day to understand how HTML and CSS work to be honest and, even if it takes you a week to get familiar and know your way around Oxygen UI I strongly believe it will be worth the investment moving forward.
Another great benefit with Oxygen is that it comes with
full Woocommerce integration, allowing you to fully customize your online store as you want...
From a performance perspective, the comparison is NOT even close, with Oxygen, you have full control over what´s been inserted on the theme and, therefore, on the DOM...
Oxygen also offers...
Full
Gutemberg Integration - This feature doesn´t get enough value. If you´re running a Marketing Agency and offer Web Development/Design, Oxygen offers the opportunity to build pages/sites and export it as Gutemberg block or template you can import on your client´s and, the best part is, they don't need to have Oxygen install on their end. Secondly, you can also
set permissions as to the extent the client can edit or change any of the designs elements.
Lastly, the pricing structure of Oxygen is also something worth mentioning as I believe it´s a complete steal and bargain in comparison to other "websites" builders out there like Elementor, WPBakery, and Divi...
Their most expensive plan costs $229 at the moment and it gives you, not only full access to ALL modules but, also, lifetime support and an unlimited license to use on as many WordPress installations as you want.
Oxygen as many other features you might find interesting but it requires a deeper knowledge of CSS but, these are the ones I believe is worth mentioning for someone NOT familiar with it.
Give it a try, I am sure you will find a nulled or free version of Oxygen somewhere around this forum or buy the product and test it for yourself and, if you´re not 100% satisfied with it Oxygen offers a 60-day money-back guarantee policy.
Cheers and stay safe!