Gaia GPS has improved a lot recently. It has the best selection of maps and aerials available on iOS (I haven't used Backcountry Navigator) and still has Google maps (other apps seem to be dropping them). I don't like their navigation screens as much as some, but you can download lots of stuff for offline use. It's very customizable. You can pick a POI and choose either a standard GPS like navigation to it, or choose driving directions and it throws you into a road map. It also allows you to open POIs in Theodolite, which is another cool app (augmented reality theodolite). It also can sync to GaiaCloud, which can keep track of your stuff and sync with other devices. You download by navigating to an area on the map and selecting part of it. I like this so I can limit what I download.
The Trimble apps are also improving. I like their forestry road overlays, and even though I'm not a hunter the weather and tracking stuff can come in handy (never know when you might need the blood trail feature...). They, like Gaia, have a subscription service. And they offer a trial period. For the "elite" members you also get a website that has tools for creating routes and ways to download maps for offline use. They don't have as many options for maps as Gaia, but pretty good. With the subscription game unit maps and topos of all resolutions are available. It The tool to snap to roads is very handy for creating routes through national forests and what not online, and then you transfer to the device. Their customer service was super responsive; they seem very committed to improving the apps. Their downloads are organized by state and county, so you can download all the topos and layers of a particular resolution for say Pershing Co, NV.
Don't know about Mexico, but Gaia has Canadian maps. Haven't checked into Trimble.