The producer - who wrote the song - revealed that each version is completely different and described Lewis's version as "an X Factor ballad".
Asked which version of 'We Found Love' he preferred, Harris told Kiss FM: "Erm, they're very different because [Leona] sings it dead softly, you know, how Leona sings."
He added: "It's more like an X Factor ballad."
The DJ revealed that he still has a copy of Lewis's 'We Found Love', adding: "The only people that have got it are me and Leona Lewis."
Harris released his third studio album 18 Months earlier this week and the collection is currently leading the midweek chart.
Watch the music video for Rihanna and Calvin Harris's 'We Found Love' below: