The best known part of the story is almost certainly not history. The Primary Chronicle tells that Vladimir received missions from Muslim Bulgars, Latin Germans, Khazar Jews and Greeks, questioned each, and then sent his own envoys to observe worship in their lands. They found no beauty among the Bulgars and no gladness among the Germans, but at the liturgy in Constantinople they did not know whether they stood in heaven or on earth, and reported that God dwells there among men.
The chronicle was compiled well over a century after the events and is a work of religious and dynastic argument as much as a record. The examination of the faiths follows a literary pattern found elsewhere, the rejections are shaped by later polemic, and the reported reasons for declining Islam and Judaism serve the chronicler's purposes neatly.
None of that makes the passage worthless. It is excellent evidence for how the church of Rus understood its own origins in the twelfth century, and for the standing of the Constantinopolitan liturgy as the argument that could be relied on to persuade. The atlas records the conversion as attested and the testing of the faiths as the chronicler's composition, because a reader who meets the story deserves to know which part is the event and which part is the telling.