The discrepancy between these two recommendations is massive, in terms of cost:
GaiaGPS ... about $30/year.
Pocket Earth ... about $10 for the “Pro” version
There are literally hundreds of Adroid and/or iOS mapping applications out there that cover all the requirements. I don't understand what is the extra value in $30 per year, in GaiaGPS vs a (one-off, I presume?) payment of $10 for Pocket Earth. And I know of others that are even cheaper, but still have all the functionality required.
What's the value of the $30 per year subscription? That really adds up, over time. But even just in the first year, it is several times the cost of many other apps that do all that's required.
I assume that includes access to some sort of special maps that can't easily be used in other apps, perhaps?
But then are those maps really worth $30 per year, when there are many free map services about these days? Not just OSM and related, but actual high quality government generated map services in most states that are available using open standard map services for free. And these can be loaded up into any standards-compliant application for viewing (and/or downloading).
This is a genuine question, as I've never used GaiaGPS, so I really don't know.
(Disclaimer: I am the developer of another iOS mapping app, not mentioned yet in this topic, so I am VERY biased.)