Edward
The question you face is almost the classic SEO conundrum. Execute the consolidation poorly and you end up losing a lot of rankings and traffic. So it has risks and the first rule is do no harm.
I am what you call a hardliner however. I would consolidate. An eCommerce site doing well www.cottonon.com may be worth viewing. Same issue - global in different markets. One domain. Killing it.
Focusing on one domain long term will have significant benefits.
https://moz.com/blog/2-become-1-merging-two-domains-made-us-an-seo-killing
https://moz.com/blog/rebrand-or-redirect-my-site-consolidate-multiple-sites-whiteboard-friday
That said you have to consider it carefully - map out pro & cons etc. Move slowly and execute brilliantly. Certainly worth keeping on the radar. I would educate myself - talk to more people and then make a decision.