It really is a matter of personal preference and cost. Online will cost more, and as others have mentioned, it may not have all of the features to support your business.
Online is more convenient for collaborating. Like this is the main feature I think makes it a great product. Meaning if you need to share your books with your CPA often, online will make that WAY easier than desktop. When I used desktop, I was always scared of moving those large files across the internet, both because of security, and because I was afraid I would accidentally mess up the restoring of the file when it came back from my CPA. Online is way more secure.
The other issue to be conscious about is online is not goof proof. Yes, they backup data to their servers and such, but let's say you accidentally unreconcile the wrong account (like I did once), you can't "close it" without saving because QBO is always saving.
The problem I ran into when I sold my business, I didn't want to maintain a QBO account for an old business, so I tried to move the data back to desktop, which really didn't work very accurately, so if you do want to "switch back", it's not going to be easy or accurate so you will have to either start a new file, or do some creative stuff to portage your data back over to desktop, but it won't be the same level of continuity. Moving from desktop to online was seamless, however.
Hope that helps.
