ERP systems can be broadly classified into three tiers based on the total cost of ownership (TCO), scalability, and functionality.
Tier 1: The main players in the tier 1 category are SAP, Oracle, Microsoft dynamics, and Infor. The tier 1 category for a long time has been a two horse race between SAP and Oracle. However, of late, Microsoft dynamics and Infor have been considered by many as tier 1 ERP systems, including Panorama consulting. The TCO is extremely high and revenue is typically measured in billions of dollars. These ERP systems are best suited for fortune 1000 companies which have a global presence. Implementing the ERP system is an extremely complex procedure and requires highly skilled professionals.
Tier 2: ERP systems which fall under this category are best suited for mid-size companies. Main players are Epicor ERP, Sage, Exact, IQMS. These systems are not as complex as tier 1 systems, but they are often robust and agile enough to fit the needs of mid-size organizations. Tier 2 vendors are usually limited number to a few number of countries or regions.
Tier 3: There are many players in the tier 3 category, and they are mainly suited for smaller than medium sized businesses. Revenues typically range from $10 million to $100 million. They have limited functionality and are often designed for a vertical industry.
http://www.compudata.com/difference-between-erp-tier-1-erp-tier-2-erp-tier-3/