The issue of whether or not an account from Exact e-Synergy in Macola ES is more an issue of whether or not a customer code has been assigned in the financial section of the e-Synergy account card than it is of the account type. Even a lead in e-Synergy can show up in Macola ES if you assign a customer code (however, in Macola ES that lead will indicate that it is an associate, not a lead. I have no idea why).
There is also value in using the Suspect-->Lead-->Prospect-->Customer categorization from a sales process perspective. For example, Suspect could refer to a generic marketing list or "cold lead". Lead can be used for accounts that are actually being pursued. Prospect would be an account that you expect to do business with.
There is also a background job BLCustomerStatus.exe (doc 00.810.575) that can search for leads with a sales forecast and automatically convert them to a prospect. It also does some other neat things that are described in the above document and in the e-Synergy Implementation Manual: System Configuration.