The Subway, Bus, and Tour maps are scaled to online maps and offers more detailed information than the online maps, along with the offline map bring you a peace of mind when you know where you are when internet is not available when you are in the city of Barcelona!
By using the phone ofline, your phones battery can last a lot longer.
The points of attractions carries information such as the rank of popularity, visit durations, etc., and can be searched the plotted on the map by key word or category.
You can do a lot more with the app such as recording then sharing your trips as named trails with friends, displaying your friends locations, contact sharing, note keeping, timer, fitness etc.