Legacy form fields:
Difficult to spell-check - requires macro
tab from field to field
Cannot place bullet or numbered lists in field, can have fields in bullet or numbered lists
Cannot keep from entering carriage returns although you can keep more than one line of text from displaying.

Content controls:
Spell check automatic unless you take big steps to stop it.


Click from field to field
Can place bullet or numbered lists in Rich Text form field
Can keep plain text fields from accepting carriage returns

One other method you might want to examine is the MacroButton Field prompt. [Click here to type Name] It is used in a non-protected document (Word 97-2010) and typing replaces the field.
You go to the next field by either clicking on it or pressing the F11 key. Contents can be anything and you are limited to one line of text for the prompt.