There are 2 reasons to use QB Online instead of QB desktop.
First, you need that invoice-as-you-go feature. QBO has a nifty app that allows you to invoice from your cell phone or tablet. Imagine standing there, talking to your customer, casually tapping on your phone or tablet, and then sending the invoice on the spot. Your customer receives it almost simultaneously (depending on the internet, of course.) Wild.
Second, you know nothing about QB, or accounting, and your accountant is probably going to need to interact with your data more often than not. Using QB Online allows you to do the invoicing, and leave the bookkeeping to the pros. You should then have or quarterly meetings with your financial people and learn to read the reports. If and when your business gets too complicated for QBO, you can switch to desktop. However, I expect they will expand the online capacity as time goes by. Once you get used to the anytime, anywhere flexibility, it is hard to give up.
To me, QBO is actually Intuit’s most intuitive product. I call it the kindergarten approach because it uses large simple fonts and bright primary colors, and is generally not scary. When you log in, you are greeted immediately by easy-to-understand graphic representations of your most recent history. The two most immediate functions are a snap to figure out: how to make an invoice, and how to receive money on that invoice. With a little training, you can learn to navigate to the various places you need, and even customize your invoices, etc.
This is not to say you can’t mess it up, like desktop! Just that the basic functions are more obvious, er, intuitive.