Google maps works offline in most countries. I wouldn’t have survived my International trips without it. I’ve used Google map for public transit in many countries. Most time I get SIM card while travelling just to use Google maps.
When I've used it in the past, the offline maps kind) weren't very dependable.
They expired after 30 days (not 30 days of being offline, just 30 days from when you downloaded the map). If you had internet when they expired, the map would refresh and you'd be good for another 30 days. If the 30th day happened to be the first day of your trip, you were SOL until you found wifi.
Some of the other annoyances have been fixed (initially they only supported navigating to addresses, not business names). Some of them haven't (still no walking directions). But if I can't count on the maps to actually be there when I need them, nothing else matters.
I've tried both Google and HERE maps when traveling to a number of countries, and found HERE significantly better offline. It was constantly able to detect my exact position and update it as I kept walking, while Google Maps were quite inaccurate.
