Living in the US, it's not feasible for me to do so. Things vary widely all over the world so what I know about using radar detectors in the US and Canada often doesn't apply in other countries. Additionally, testing international radar detectors here in the US doesn't tell us much.
Around the world there's different radar detectors not sold here, different radar guns, frequencies being used, and even international firmware versions which makes the same detectors behave differently. Not to mention there's different laws and enforcement tactics used around the world. Since I don't have the same international radar guns here in the US, there's no way for me to test international radar detectors designed against those threats.
While I have tested a few international radar detectors here in the US, I've found that they're not optimized for the States, they don't do a good job of filtering out cars and BSM falses we have here, and ultimately I can tell they're not a good fit here. However, that doesn't tell me much about if they're a good fit for other countries where the driving conditions are completely different.
Since this isn't something I'm able to properly test myself, I typically refer to others who live and drive in your country and am always hoping more people step up to test and share what they find in their countries.
Here's a few resources you can check out:
New Zealand: Check out this article
Russia: RD-forum.ru
Spain: Todoradares
General International Discussion: International area of RDF
If you'd like to know more about what works best in your area, I'd like to invite you to start testing and sharing your results too. We really need more people around the world helping and sharing information.