Choosing between purchase order systems is presented as a feature comparison and is better treated as a sizing exercise. Three facts about how your organisation buys decide which shape of product fits, and once you have them the shortlist is short. Getting the sizing wrong is the expensive error here, in either direction.
The three facts
How many orders you raise a month, how many people raise them, and how often a delivery arrives incomplete. Low on all three and the module in your accounting package is probably enough. High on the second and third and you need line-level receipt tracking. High on all three with a dedicated buyer and a suite starts to earn its keep.
Why partial deliveries are the pivot
They are what document-level tracking cannot represent. If deliveries almost always arrive complete and on one date, an order is effectively a single event and simple tools cope. If they arrive in pieces over weeks, the order is a running account and needs quantities per line, which is where cheap tools stop being adequate.
What to insist on at any size
Automatic unique numbering, approval before issue, receipts recorded by whoever takes the delivery, dated revisions and an export you can read without the vendor. All five are cheap in any product and expensive to add later, and the last is the one people forget until they want to leave.
Questions people ask about purchase order systems
Should we shortlist by industry?
Rarely. Industry products matter where the buying itself is unusual, such as construction retentions. Otherwise sizing matters more.
How much should this cost?
It varies by shape, so decide the shape first. Comparing an accounting module against a procurement suite on price is not a meaningful comparison.
Can we change later?
Yes, and moving up is easier than moving down. Clean data and a readable export make any future move cheap.