According to the Primary Chronicle (a 12th-century Rus text), he considered Judaism (from the Khazars), Islam (from the Volga Bulgars), Western (Latin) Christianity (from the Germans), and Eastern (Greek) Orthodox Christianity (from the Byzantines). Vladimir rejected Islam for its prohibition on alcohol and pork, Judaism due to the Khazars' loss of their homeland, and the Latin rites because they were too austere.
I wonder how the different religions were presented to him. I imagine that there would be bias from the people presenting, maybe they tried to change his mind when he was considering one other than Christianity because of the person's presenting biases.