Hemi heads are mainly special as a marketing advantage which is not used by other companies whose heads in the past may also hemispherically shaped…like BMW and others. The debate about which is better is a debate about straight six and v six and which is better. They each have their own advantages and there are other shapes that manufacturers have thought were better for their purposes.
So, have their been six and even four cylinder engines with similar heads ? I am sure there have been plenty.