What are the major differences between Requests for Proposals (RFPs) and Requests for Qualifications (RFQs)? Should a public art agency use one instead of the other?

Members of Americans for the Arts have endorsed RFQs above RFPs and consider RFQ’s best practice, because RFQs have been more efficient and effective in producing high-quality public artworks and are generally seen as being more fair to artists.
Requests for Qualifications ask artists interested in a commission to submit information about their training, previous work, and other forms of evidence of their ability to create a public artwork. Requests for Proposals ask artists to develop and submit their ideas for a commission. Both options have advantages and disadvantages for artists and arts agencies, and both try to strike a balance between giving the artist a free hand and also ensuring that the artwork produced is desirable and appropriate to the public and commissioning agency.