I don't see how you can possibly target the second group of clients with a startup. Organizations in the second category will by-and-large have the following properties:
A) Already have an ERP implementation of some sort. It may be awful, and difficult to manage, but it's there and most likely interfaces some important, or even mission-critical systems in the company. It's much easier to sell to an organization that is transitioning from ad-hoc/manual ERP to a systematic approach than it will be to convince to replace SAP with your new stuff.
B) Be relatively risk-averse. Larger organizations just have more to lose from a failed implementation. In a SMB, ERP often replaces manual process which can be reverted to or extended in case of a failed implementation. At a larger organization, you'll have mission critical processes interfacing with the ERP system meaning that there's very much an "if it's not broken..." attitude.
C) Classic high-touch, expensive enterprise sales cycles. While there are startups which have managed this, it's definitely the harder nut to crack than the more high-volume, but shorter, sales cycle that you'll find in the SMB market.