QuickBooks Sync by MyWorks

Pros:

Features that other Shopify/QB apps don't offer, which saves manual work if you use locations & classes. Before we had to use an app to export the orders, then modify them and then upload.
Also being able to sync inventory from Shopify to QB is great.
Helpful team that will go above and beyond to help setup and rectify issues.

Cons: No live chat, so it can take some time to resolve issues.