Exchange 2010 Standard or Enterprise

Hello, I try to find out what Exchange edition 2010 (Standard/Enterprise) are the  best chose. I have currently a small shared hosting service (around 200 domains) controlled by Hosting Controller.
The information that I find on the internet is very confusing.
¿Can help me someone?
 
Thank You!!
Marcos

The functionality at client end doesn't have any big different if you are using Exchange standard or Enterprise CAL.
At Server end the major difference in my point of view is the number of Databases, i.e in Standard version you can create upto 5 databases and in Enterprise 100 databases. 
Other difference listed in this link
http://www.microsoft.com/exchange/2010/en/my/Licensing.aspx
 
In early stages it would be a good choice to go with Standard edition to reduce initial cost of the services.