As a frequent traveller I can say Google Maps (offline mode) sucks!

If you are fully offline, then it works as intended.

However, if you have even a tiny bit of connection, even if your connection is spotty or very slow, Google Maps refuses to use its offline data, crippling the experience and making it unusable.

I agree with the sibling comment. When I travel, I usually use 3 apps and download the offline maps of the regions I visit: Apple Maps (for iOS apps and embedded features), Google Maps, and thank god: Organic Maps.