Hi, I think the one to be copied to the other may have existing indexing in Google, so in general speaking it should have better ranking already but depends on domain weight too...i think if possible, you'd better not to 100% do copy & paste because this could cause duplicate contents cross the different domains, they are competitor pages to Google, as google doesn't know they are belonging to same company. therefore, it could cause some ranking up and down, but i think it;s minimal..
my suggestion is: from seo perspective, choose which domain or page is more important to you, focus on that domain./pages on content creation and link building...or.. if you have time and energy, you could do different contents each time which i think is not realistic..thanks Boson
