There are lots of advantages using cloud based software. For one you don't need to tinker with hardware. Means you also save time hiring IT guy to fix system issues and so on.

Think of these kind of indirect cost when you are evaluating any cloud based SaaS.

As for accounting, make sure you can manually backup the data yourself. It can be backup to another cloud where you can download the data anymore.

Also, for those fearing data stolen or other security stuffs. There a lots of security features in place that can reduce chances of data getting stolen. Even if you do it on premise also can be stolen.

End of the day, you need to weight the pros and cons. Personally, I am pro cloud. I do not see what is the big issue about data security if it is managed well.