It merely depends on what you need. Both versions have their advantages and it is on you to choose the mode that suits your business.
There are two main advantages of the Offline mode - much faster data storing comparing to the same process in online mode and the ability to work without internet in majority of functions connection. However, there are certain disadvantages like overwriting data if you work on more than one device e.g. your mobile and the web application or two or more mobile phones and/or the web. Simply, each device creates its own back up and overwrites the data. As a consequence the data are not exactly the same on each of the devices as every one of them retrieves the data and creates its own copies.
Advantage of the Online mode over the online mode is the multiple use of the app on numerous devices. You can create managers with limited privileges. The back up is created on the server first and then the same data are sent to each of the devices. This way, all the data is synchronized over all devices simultaneously and in the same content. The flaw of this mode is that the data will not be saved if there is no internet connection.