Old Professional vs New Professional vs Enterprise

Old Professional vs New Professional vs Enterprise

We are currently using the Old Professional version of zoho crm and have 39 users.  We had 40 users recently during our CRM Plus trial and when we tried to add a new user our system said that we could not have more than 40 users.  

What is the user limit for the Old Professional version?

What is the user limit for the New Professional version?

Also, we are unable to add anymore pick list fields to our system.  Would moving up to the New professional or Enterprise version give us the ability to add more fields with pick lists?

I need a complete breakdown of what each version offers.