Desktop all the way. From an accounting side, Quickbooks Online is less user friendly and also far more likely to let your clients persist in bad accounting behavior that will result in a costly cleanup at the end of the year. And on the other end of the equation, I've met several business owners/users who have made the switch from Desktop to Online over the past four years, but not a single one who didn't regret it afterward.
Try Freshbooks. Robust as QB desktop is, it becomes too bulky. As I understand Freshbooks, you only pay for the parts you need.
Since a client turned me onto Freshbooks, I started recommending it. I continue to hear people having problems with QB desktop or on line even worse.
I told a client about the different software and the feedback I get from other clients as well as the reports I get from the different software. He did not listen and decided to do a 30 day trial run of each side by side. Within the first week, he sent me an email telling me others were correct. He abandoned QB and uses Freshbooks.
I have used both versions, but was much satisfied with the Desktop version’s feature set. It ease work. Also, now I am hosting it on a cloud server, the hassles regarding the cloud server setup and IT stuff is taken up by the company which is providing the hosting services.