First, I think your confusing yourself. A PMSI is simply another type of security interest, which actually requires its own filing in order to achieve perfection.
It is obviously a confusing topic. My understanding is that a PMSI (in non-inventory) filed (perfected) within 10 days is superior to all other claims (made before or after). I have seen at least 1 Wiley test question that involved this as an explanation, but honestly I have nowhere to point you in order to prove this. If Im wrong Id love to be corrected…but Im pretty sure this is how it works. Regarding PMSIs in inventory,
“The importance of a PMSI is that it provides the seller of goods on credit (“Seller”) with priority
over other creditors who have a conflicting security interest in the same goods. The typical situation for
Seller will be sales of goods on credit to a customer for the customer’s inventory when the customer’s
primary lender already has a perfected security interest in all of the customer’s subsequently-acquired
inventory (typically this will be in the form of a “blanket” security interest in after-acquired inventory,
equipment, accounts receivable, furnishings, etc.). If Seller follows the very specific steps to obtain a
PMSI for the goods that it is selling to the customer it will be able to trump the security interest of the
other creditors. A properly perfected PMSI will have superior rights to the specific inventory the Seller is
selling to that customer and to certain identifiable cash proceeds from the inventory over a conflicting
security interest in the same inventory.”
https://www.nationalcorp.com/ncr/file/index?filename=PMSI_SecurityInterests_Oct_08.pdf (also has an interesting example)
Its saying that it works the same way with inventory. Id just remember that a PMSI needs to be filed within 10 days of purchase of inventory (or non-inventory) in order to be properly perfected. A properly perfected PMSI beats all others, except a buyer in the regular course of business (but I will bet a dollar that they never put a buyer in the course of regular business into a question dealing with the power of a properly perfected PMSI).
Better be right, taking REG tomorrow! Pray for me my friends