TL074 is the low noise member of this series, TL084 is the low power member. The main difference is that the TL074 datasheet mentions “Vn = 18 nV/√Hz” in the feature summary, while the TL084 datasheet mentions “1.4 mA/ch typical”. For the other you have to look under electrical characteristics to find exactly the same value. I haven’t compared all the graphs, but odds are they’re the same silicon these days.
EDIT: The latest datasheet revisions (November 2020) have identical summaries; they both mention low power and low noise, with the same specs for both.