10.22Minor 7 is usually softer than dominant 7

Compare:

Dm7

D F A C

with:

D7

D F♯ A C

Only:

F → F♯

changes.

Yet:

Dm7 often functions as ii in C.

D7 strongly wants to go to G.

The third changed the harmonic function.

This is a great example of why thirds matter so much.