Question about Nokia Smartphone OSes.

How different are the three Nokia OSes SymbianOSv9.4, S60 and Maemo 5?
Do they impact the ease of getting the phone to function as an email alerter?
I need to get a phone that can give an audio signal every time I get an email, probably for a gmail account, and the choice at first seems to be between the C6 the N97 and the N900 (with the SymbianOS, S60 and Maemo 5 OSes, respectively).
Does anyone have experiences with similar uses of these or other such devices?

Refining the search: (took hours): Seems like the Choice is between E5-00, C6 and E72… experiences with these particular device also appreciated!