I also use them for file integrity checking, but I frequently check large files, e.g. 50 GB files, and in that case the difference in time until finish between "sha256sum" and "openssl dgst -r -sha256" is extremely noticeable on a Zen CPU.
On the other hand, on older Skylake/Kaby Lake/Coffee Lake etc. CPUs, both programs have the same speed.
Thanks for the info! Fortunately for my purposes of integrity checking, slow is okay.