let us see the difference between exchange 2010 editions,
Exchange server 2010 Standard Edition
The main difference between two editions is that Standard edition only supports 5 database stores. This can be a major issue with medium to large companies as Microsoft recommends only 100-200GB max per data stores. This version is ideal for CAS and HUB server role for medium to large companies as Enterprise edition will not provide addition features on these server roles.
Exchange server 2010 Enterprise Edition
Enterprise version supports 100 mailbox databases compare to standard. Enterprise edition is a must have for mailbox server role in medium to large companies.