There are, as you know, many versions of the same product. It's hard to track inventory or run reports if you're using 3 different manufacturers versions of say, a spray oil, or a nutrient. To solve that issue, set your preferred products and then you'll always know you're picking the right one.
Step 2: When you go to the My Products tab, you'll see the ones that have been marked preferred:
When one of the products is typed in (on the record, recommendation, and on the PO) it will be at the top with an asterisks and you'll all be consistent with which one is chosen. The only potential issue is if the product your 3rd party advisor writes the recommendation for says 32-0-0 but your preferred is the 32 0 0, you'll have a difference. You can always go into the record and switch the product if need be. Or just ask them to write it to the other version in the future.