I know the following facts about "People or Group" column type:-
Inside the built-in New & Edit forms they will be rendered as auto-complete fields.
Inside custom forms they will be rendered as a simple input field (without auto-complete) but with a People picker capabilities.
As an additional note I want to use the built-in forms since it will allow me to add new columns to all the built-in forms when I add it to the content type.
Now this leave me in trouble as I am using the built-in forms, because users are complaining that they do not know who are the users they need to auto-complete against.
Let say I have a
People or group named
Account manager , so users need to know the Account Managers they need to select from and this is not possible with the auto complete feature.
Of course the auto-complete is useful but without a people picker capabilities this will not be very useful in some cases, for example in outlook you got the 2 options when you want to send an email to someone, you have both auto complete & People picker.