[improbable22]

Some of them make downloading more of a hurdle than others, insisting that you download a whole country, or figure out what region you want.

On MapOut at least, you zoom in too far & then click the tile you don't have. On a good network there's a little more friction than on (say) google maps, but not so bad. A few MB, never hundreds of MB.

(And on a bad to nonexistent network, it's golden to be absolutely sure that it still has what you looked at yesterday.)