As someone who started testing things with UBI images, I have found them to not be that great in terms of predicting how things behave installed under CentOS or RHEL. There are a lot of seemingly minor packaging differences that cause annoying issues when you go to deploy the same stuff on a real RHEL box.

And as i said the rhel images for docker and supported packages in the registry is very very limited, you will miss a lot of packages.