I've had the experience of using Ezoic, Monumetric, and Adx via reseller. Currently I'm only using Monumetric and Reseller Adx though.
My experience with Ezoic was a few years ago so I don't really know their current performance. But Iike many people, I didn't have a good experience with them.
For my website the RPM was only slightly better than AdSense. Not sure if it's a language barrier or anything but their customer support felt condescending and borderline rude.
On the other hand, Monumetric is a hidden gem. Customer support is responsive (relatively speaking) and they pay on time. I paid the $99 fee and make it back within a month.
My custom AdX setup used to outperform Monumetric in terms of RPM.
But since they added video ads on my site, it has now beat my own AdX setup.
But note that I'm using reseller AdX and Monumetric on two separate sites.