When should a percentage be written as a percentage and when should it be written x out of n?
Two comments. First: the "frequentist" format appears to be easier to understand than the normed percentages, at least if information needs to be chained as in Bayesian reasoning. On the other hand, probably normed percentages are easier to understand if two fractions are to be compared. 
Second, I'd say that you should only use percentages if your sample is large enough. For example, "4 out of 5 respondents" amounts to 80% but the latter figure would probably suggests higher confidence than is warranted, given that it is really only a single respondent away from 3 out of 5 (60%)…