By the docs of RHEL
The legacy rhel7-minimal (or rhel7-atomic) and UBI ubi7-minimal images
are stripped-down RHEL images to use when a bare-bones base image in
desired. RHEL minimal images provide a base for your own container
images that is less than half the size of the standard image, while
still being able to draw on RHEL software repositories and maintain
any compliance requirements your software has.
BOTH
- Includes Microdnf.
- Not YUM.
ATOMIC
UBI-MINIMAL
I personally would choose UBI-Minimal, but, think you should also take a look at the UBI FAQ to know the details, pros and cons of each image depending on your business - https://developers.redhat.com/articles/ubi-faq#ubi_details