Exchange 2003 OMA or OWA?

My company has Small Business Server 2003 with Exchange and wants to upgrade to using smartphones (WM 6 professional). We use public folders for company contacts and create a new folder with each new project. I want the ability to use one device as easily as possible for as much as possible. It would take longer to access public contacts by using OWA. I intend to use a gps service that will input address from the contact in outlook.
I need to have an alert when new emails come in. I am unaware if this can be done with OWA.
Concerning these issues is OMA a better choice and can handle public folders? I have a PDA synced to my desktop and it is WM 6 classic but outlook does not sync multiple contact folders or public folders.