With so many to choose from, sometimes deciding on which persistent identifier scheme to use can be difficult. At the Publications Office of the EU we are responsible for identifying content coming out of the EU institutions. We are a registration agency for established international identifiers such as ISBN, ISSN and DOI as well as providing support for our own EU-specific persistent URI scheme. When we received a request from one of our clients for help in identifying the content of a historical archive, we asked ourselves the question: what would be best in this specific case: the doi or our own persistent URI scheme, data.europa.eu? So we have decided to launch a small study to compare the two approaches according to the requirements of this specific case. The results will be known by the end of the year and PIDapalooza would be the ideal forum to share the conclusions.