While mean scores from Likert-type scales can be compared across individuals, scores from an ipsative measure cannot. To explain, if an individual was equally Extroverted and Conscientious and was assessed on a Likert-type scale, each trait would be evaluated singularly, i.e. a respondent would see the item "I enjoy parties." and agree or disagree with it to whatever degree reflected their preferences.
If the same traits were evaluated on an ipsative measure, respondents would be forced to choose between the two, i.e. a respondent would see the item "Which of these do you agree with more strongly? a) I like parties. b) I keep my workspace neat and tidy." Ipsative measures may be more useful for evaluating traits within an individual, whereas Likert-type scales are more useful for evaluating traits across individuals. Additionally, ipsative measures may be useful in identifying faking.
In education, ipsative assessment is the practice of assessing present performance against the prior performance of the person being assessed.