Exchange Mailbox Provisioning or Use a script?

Hi,

 I have configured FIM to sync and provision AD users in my my domain (Contoso), but I haven't got around to doing it with Exchange. I know how to mailbox enable AD users with scripts, but not how to Exchange provision users in FIM 2010 R2. I'd like some advice on the following:

1. I have input CSV files with the following details: username, first name, surname, email and objectsid
2. I've used fim to sync these details with Contoso to provision users into a particular OU
3. I can make changes to my CSV file and sync the changes to Contoso users

What's the more robust\straight forward approach in terms of Exchange provisioning? Given that I already have users in Contoso's AD, am I better off simply using scripts or going down the FIM Exchange provisioning route?

Thanks