Comparing Two Data Sets and Finding the differences?

I have two reports that can be pulled from two systems at work: 1) our normal inventory reporting system and 2) a production software that tracks where in the process a particular part or widget is at; we are in the process of fully implementing this production software and making sure that both reports are integrated with one another (what appears or is entered in inventory as a customer order also appears in the production software and vice versa). In both softwares/systems, I can see the purchase order from the customer, the part number, and the quantity. In the production software, I also have the work order we've assigned internally.

However, my issue is that the two systems record quantities in different ways. The inventory system records the quantity 1-by-1 so one row is 1 unit of measure. The production software groups the quantities by what step in the production process the parts are in for that particular customer order. Sample data below.

Inventory System:

Production System:

I am needing to reconcile the differences between these two datasets in a cleaner way, so we can identify what orders are missing in what system, or what quantities, etc. For reference, the inventory system has ~15,000 rows and the productions system has ~600. When we've finished implementing the new production software, the totals quantities between the two softwares will match when fully integrated. Just needing to identify the differences so we can track down the particular issue as to why/why not it does not show in the other software.

I compared the two using two PivotTables and an INDEX/MATCH, but am looking for something cleaner and more succinct, almost like a report. I tried feeding the two through PowerQuery, but merging the two datasets results in... a mess.

Any ideas or direction? Open to PowerQuery, PowerBI, whatever. I'm using Office 365.