Always start with the business case, the strategy

before you get wound up to upgrade, stop, take a breath, and ask the right question first: Where is our business going, and how should we transform? The ERP decisions will flow from this and not vice versa.

Also, beware of vendors that are focusing on profits and cash-flow and so cut spending on innovation:

Check if your current ERP vendor has undergone a material change of control. For more on a material change of control, see this Diginomica piece. New owners may take ERP innovation in different directions or may curtail needed innovation investments. Some ownership changes, like the appearance of private equity firms or activist shareholders, can radically alter one’s relationship with an ERP firm. In the last decade, we’ve seen a number of these changes and their effect on ERP product lines and management.

Original source: Assessing ERP upgrades in the 21st century